LIBRARY 
OF  THE 

UNIVERSITY  OF  ILLINOIS 

NORTH  CAROLINA  BOARD  OF  HEALTH. 


SANITARY  ENGINEERING, 


THIRD  EDITION. 


BY 

c_  e.. 

Former  Member  or  the  North  Carolina  Board  of  Health. 


THE  LIBRARY  OF  THE 

NOV  11  1938 

UNIVERSITY  OF  ILLINOIS 
RALEIGH  : 

P.  M.  HALE,  State  Printer  and  Binder. 
1885. 


PRESSES  OF 

E.  M.  UZZELL, 

RALEIGH,  N.  C. 


SANITARY  ENGINEERING. 

(THIRD  EDITION.) 


By  WILLIAM  CAIlSr,  C.  E. 


CHAPTER  1. 

GENERAL  CONSIDERATIONS. 

It  is  only  within  the  last  few  decades  that  Sanitary  Engineer- 
ing, which  is  concerned  with  the  proper  methods  for  the  dis- 
posal of  the  refuse  of  our  towns  and  cities,  has  claimed  the  con- 
sideration of  scientific  men,  although  its  importance  has  been 
recognized  from  the  earliest  times — in  fact  so  soon  as  men  began 
. to  congregate  in  towns  and  cities  or  even  in  encampments.  The 
light  which  modern  chemistry  sheds  upon  chemical  reactions  and 
. decompositions  and  the  practical  value  of  the  extended  researches 
^in  the  laws  of  the  flood  of  liquids  and  gases,  form  the  data, 
together  with  recorded  experience,  by  which  the  modern  sanitary 
engineer  devises  systems  of  sewerage  to  meet  the  wants  of  any 
community. 

^ Death  eates  lowered  by  sanitary  works. — We  are  told 
^ upon  the  best  authority  that  in  England  there  occurs  annually 
upwards  of  four  million  cases  of  preventable  sickness;  and  that 
^ 125,000  persons  are  prematurely  cut  off  every  year  from  a neg- 
^ lect  of  sanitary  precautions. 

^ Now  if  this  be  true  in  a country  which  has  adopted  the  best 
^ known  sanitary  precautions,  at  great  expense,  how  much  more 
significant  will  the  records  in  this  State  appear,  where  the  only 
‘^outlay  that  may  be  classed  under  the  head  sanitary^’  is  gen- 
^erally  made  in  meeting  doctors^  hills,  diud  funeral  expenses? 

It  is  further  stated  that  in  England,  since  the  sanitary  precau- 
tions  have  been  instituted,  that  the  death  rate  has  been^  lowered 


4 


SANITARY  ENGINEERING. 


by  from  cne-fourth  to  one-tliird,  and  is  besides  decreasing  from 
year  to  year.  The  following  table,  referring  to  a few  localities 
in  England,  taken  from  Latliam^s  Sanitary  Engineering,’^ 
speaks  more  forcibly  than  all  the  other  arguments  that  may  be 
presented,  especially  to  those  who  have  paid  but  little  attention 
to  sanitary  subjects,  and  are  inclined  to  be  skeptical  as  to  the 
great  actual  saving  of  life  that  may  be  attained  : 


Name  of  Place. 

Population 

in 

1861. 

1 Average  mor- 

1 tality  per  1,000 

before  con’tion 

1 of  works. 

1 Average  mor- 

1 tality  per  1,000 

I since  complet’n 

1 of  works. 

Saving  of  life. 

Per  cent. 

Reduction  of 

typhoid  fever. 

Rate  per  cent. 

Reduction  in 

rate  of  phthisis. 

Per  cent. 

Banbury 

10,238 

23.4 

20.5 

12^ 

48 

41 

Cardiff, 

32,954 

33.2 

22.6 

32 

40 

17 

Corydon,  

30,229 

23.7 

18.6 

22 

63 

17 

Dover,  

23,108 

22.6 

20.9 

7 

36 

20 

Elv, 

7,847 

23.9 

20.5 

14 

56 

47 

Leicester, 

68,056 

26.4 

25.2 

48 

32 

Macclesfield, 

27,475 

29.8 

23.7 

20 

48 

31 

Merthvr, 

52,778 

33.2 

26.2 

18 

60 

11 

Newport, 

24,756 

31.8 

21.6 

32 

36 

32 

Kugby, 

7,818 

19.1 

18.6 

2i 

10 

43 

Salisbury, 

9,030 

27.5 

21.9 

20 

75 

49 

Warwick, 

10,570 

22.7 

21 

n 

52 

19 

A previous  statement  would  indicate  that  the  death  rate  is  still 
being  steadily  lowered.  As  Latham  states,  the  most  healthy  dis- 
tricts show  but  a small  saving  compared  with  the  others;  though 
nearly  all  show  a marked  diminution  in  certain  diseases — typhoid 
fever  and  phthisis. 

Similar  results  have  attended  the  enforcement  of  sanitary  mea- 
sures in  some  of ‘our  American  cities. 

A striking  illustration  is  St.  Louis,  where,  it  is  stated,  that 
from  1867  (when  the  Board  of  Health  was  organized)  to  1877, 
although  the  population  had  more  than  doubled,  the  death  rate 
had  decreased,  so  that  actually  in  1877  there  were  fewer  deaths 
than  in  1867. 

The  average  mortality  for  this  country  is  about  20,  ranging 
from  17  to  30  in  1,000  generally;  but  St.  Louis  shows  a death 


GENEKAL  CONSIDERATIONS. 


5 


rate  of  only  11,  which  apart  from  its  site,  ‘‘must  be  ascribed 
largely  to  its  excellent  water  su[)ply  and  sewer  system.’’ 

Economical  Aspects. — Apart  from  the  humanitarian  view 
of  tins  question,  it  may  be  considered  in  its  economical  aspects: 
thus  Latham  has  taken  Croyden,  where  the  total  cost  of  sewers, 
&c.,  was  $943,800,  and  estimated  the  saving  m funerals ^ in  sick- 
ness (allowing  that  for  every  life  saved  25  would  escape  sick- 
ness, the  saving  being  estimated  at  $5  for  every  sick  person) 
and  in  the  labor,  for  years  only,  by  the  prevention  of  pre- 
mature death,  at  a total  of  over  $1,000,000,  which  thus  exceeds, 
in  the  short  space  of  6J  years,  the  total  cost  of  the  sanitary 
works. 

Yellow  Fever  Caused  by  Filth. — How  much  more 
striking  would  be  the  result,  were  we  to  take  some  of  our  own 
plague-stricken  cities  in  America?  Where  has  the  yellow  fever 
its  origmf  In  the  filthiest  port  in  the  world,  Havana,  where, 
“the  tide  being  almost  imperceptible,  all  the  emptyings  of  the 
sewers  remain  in  the  harbor  until  they  become  a foetid  and  revolt- 
ing mass  of  corruption.”  From  there  the  seeds  of  the  yellow 
fever  are  carried  by  ships  to  other  ports ; and  when  these  are 
foul,  the  scourge  begins. 

General  Butler  at  least  has  the  merit  of  having  to  a great  extent 
kept  New  Orleans  clean  and  free  from  the  epidemic  during  his 
occupancy  of  the  city.  In  1878,  however,  in  consequence  of  the 
foulness  of  the  city,  she  suffered  the  most  terrible  visitation; 
whilst  in  1879,  through  the  energetic  workings  of  some  of  her 
most  public-spirited  citizens,  in  carrying  out  sanitary  measures, 
the  mortality  from  yellow  fever  was  very  much  reduced. 

Galveston  was  kept  clean  and  escaped  the  plague.  Huntsville,/ 
Ala.,  actually  sheltered  yellow  fever  victims  with  impunity ; 
whilst  Memphis,  in  1879,  again  suffered  from  her  foulness. 

What  more  instructive  lesson  than  the  facts  just  given  ? 

Advantages  of  Keeping  Clean. — If  we  keep  clean  there 
is  less  chance  of  dying,  greater  enjoyment  of  life  from  increased 
health,  fewer  bereavements,  and  a positive  pecuniary  gain  to  the 
community,  even  including  the  cost  of  sanitary  works.  Health, 


6 


SANITAKY  ENGINEERING. 


population  and  money  values  also,  generally  go  hand  in  hand, 
when  other  conditions  are  favorable. 

On  the  contrary,  if  we  disobey  the  Divine  Will,  by  running 
counfer  to  natural  laws,  we  are  punished  for  the  sin  of  disobe- 
dience. Here  we  have  rewards  and  punishments — both  teaching 
their  own  moral  lessons.  Choose  between  them. 

Is  North  Carolina  Clean? — Let  us  now  inquire  as  to 
our  own  cleatdiness,  which,  the  Good  Book  tells  us,  is  next  to  god- 
liness. The  result  of  this  inquiry  would  be,  that  typhoid  fevers, 
diphtheria  and  certain  enteric  fevers  that  are  now  classed  as  filth 
diseases/’  are  common,  especially  in  the  larger  towns  of  the  State; 
and  that  these  diseases  are  sufficiently  accounted  for  by  bad  wellsy 
foul  yards,  privies,  and  cess-pools;  the  latter  tainting  the  air  with 
their  gases  and  the  water  with  their  dissolved  impurities. 

There  are  but  few  privies  in  the  State  that  ought  not  to  be 
abolished,  and  some  good  system  substituted  in  their  place.  It 
is  otie  object  of  this  paper  to  suggest  such  systems. 

But  it  is  not  sufficient  that  our  own  house  alone  be  free  from 
reproach.  The  individual  may  suffer  when  it  is  onl^  his  neigh- 
bors who  are  to  blame.  The  whole  community,  as  a unit,  must 
practice  cleanliness. 

The  germ  of  disease,  engendered  amid  the  surroundings  of 
filth,  if  wafted  to  the  palace,  can  strike  as  deadly  a blow  there 
as  in  the  dirty  hovel,  as  recent  examples  show. 

Filth  and  Disease  go  Hand  in  Hand. — Of  the  exact 
nature  of  the  poison  generated  by  filth  we  know  little;  but  it 
has  certainly  been  demonstrated  in  numerous  cases  that  the  rav-i 
ages  of  epidemics  are  in  direct  proportion  to  the  foulness  of  the 
locality.  Thus  in  one  city,  diphtheria  foTlowed  the  line  of  bad 
sewers,  in  another  of  bad  wells.  Bad  water  is  one  of  the  most 
efficient  agents  in  spreading  disease. 

The  cholera  of  1853,  in  London,  attacked  districts  furnished 
with  un filtered  Thames  water  with  three-and-a-half  times  the 
severity  experienced  by  neighboring  districts  supplied  with 
Thames  water  filtered  through  sand  and  charcoal. 

It  has  become,  as  it  were,  an  accepted  truth  in  sanitary  science 
that  the  fatal  effects  of  epidemics  may  either  be  prevented,  or 


GENERAL  CONSIDERATIONS. 


7 


their  spread  materially  hindered  by  a proper  attention  to  sanitary 
precautions.  These  precautions  simply  consist  in  the  having,  at 
all' times,  _pi6re  air,  wholesome  food,  and  good  water.  It  is  only 
the  first  and  last  of  these  requisites  that  will  be  considered  in 
what  follows,  as  they  pertain  more  especially  to  the  scieiice  of 
“Sanitary  Engineering’^;  though  it  is  to  be  observed  that  whole- 
some food  is  to  a certain  extent  dependent  upon  the  good  water 
or  milk  used  in  the  cooking. 

By  a disregard  of  these  pi*erequisites  to  health — and  they  are 
more  or  less  disregarded  by  us  all — we  enfeeble  the  system,  suf- 
fer a loss  of  vital  energy,  and  are  thus  fit  subjects  for  an  attack 
by  the  first  epidemic. 

The  “debilitating  effects”  of  large  cities  are  mainly  due  to  the 
poisonous  gases,  generated  by  the  putrid  matter  of  sinks,  sewers, 
&c.,  which  gases  find  their  way  into  chambers  through  faulty 
pipes  and  traps,  or  are  otherwise  diffused  through  the  atmos- 
phere. When  the  debilitated  person  seeks  the  pure  water  and 
bracing  air  of  the  mountains,  the  relief  is  almost  instantaneous, 
thus  proving  the  life-giving  qualities  of  pure  air  and  pure  water. 

The  Science  of  Prevention. — The  Science  of  Medicine, 
so  long  confined  to  the  art  of  healing  alone,  now  declares  in 
favor  of  the  Science  of  Prevention  as  the  higher  philosophy. 

Let  us,  then,  state  the  principles  of  this  latter  science  clearly 
and  succinctly;  not  entering  into  many  details,  but  giviug  mainly 
those  principles  and  facts  that  should  be  known  by  every  one. 
Any  system  proposed  must  be  a simple  one — the  simplest  is 
generally  the  best — to  meet  the  needs  and  comprehension  of  all 
classes. 

The  law  organizing  the  N.  C.  Board  of  Health  requires  a 
monthly  report  from  each  county  on  vital  statistics.  It  is  of 
great  importance  that  this  law  be  faithfully  carried  out,  so  that 
the  effect  of  the  suggestions  given  below,  where  carried  out,  may 
be  ascertained. 

The  same  act  requires  that  the  Board  “shall  gather  informa- 
tion, for  distribution  among  the  people,  with  the  especial  purpose 
of  informing  them  about  preventable  diseases.” 


8 


SANITARY  ENGINEERING. 


Disease  may  be  prevented,  other  conditions  being  favorable, 
by  a proper  attention  to  drainage,  ventilation,  water  supply,  and 
the  prompt  disposition  of  sewage  matters. 

We  shall  consider  the  subject  in  the  above  order. 


CHAPTER  II. 

DRAINAGE. 

Wet  and  Dry  Soils. — The  farmer  well  knows  that  when  a 
wet  soil  is  not  drained,  valuable  plants  refuse  to  grow,  due  to 
the  land  being  ^^co!d’’  and  ^‘sour’^;  and  that  by  drainage  such 
lands  are  often  converted  into  the  best  quality  of  lands,  owing 
to  the  replacement  of  the  excess  of  water  and  vegetable  acids  by 
warm,  dry  air,  so  that  the  roots  now  find  the  proper  amount  of 
air,  moisture  and  temperature  to  satisfy  the  conditions  of  growth. 

The  sun’s  rays  now  cause  a healthy  decomposition  of  organic 
substances,  in  place  of  the  imperfect  one  that  seems  the  necessary 
concomitant  of  moisture  in  excess;  so  that  now  neither  acids  are 
formed  in  the  ground,  nor  dangerous  organic  impurities  thrown 
off  into  the  air. 

It  is  the  latter  that  produce,  indirectly  or  otherwise,  the  inter- 
mittent and  remittent  fevers,  so  common  over  the  whole  South. 
The  best  cure  is  drainage. 

^‘The  feus  of  Lincolnshire,  in  England,  and  marshy  districts 
along  the  lower  Thames  were  formerly  greatly  scourged  with 
fever  and  ague  and  with  malarial  neuralgia.  The  extensive 
y drainage  operations  carried  on  in  these  districts  have  had  the 
effect  of  removing  these  ailments  entirely.” 

Where  ground  is  water-logged,  it  is  unfit  for  human  habitation. 

Drainage  is  especially  necessary  where  sewers  are  laid,  as  the 
sewer  gases  readily  penetrate  the  brick  walls  of  the  sewers,  and 
then  find  access  to  cellars,  etc.  A dry  soil  will  condense  enough 
oxygen  to  burn  these  gases  up,  as  vvill  be  more  fully  explained 
further  on. 


DRAINAGE. 


9 


Maeariae  Poison. — It  is  generally  believed  that  all  damp 
places,  as  most  ponds,  marshes,  swamps,  river  bottoms  subject  to/ 
overflow,  etc.,  portions  of  which,  along  the  banks , are  alternately 
wet  and  dry,  are  such  as  originate  malarial  poison,  and  must  con- 
tinue to  originate  it  so  long  as  such  conditions  hold.  The  occa- 
sional overflow  of  salt  water  aggravates  the  evil,  as  also  the 
accumulation  of  leaves,  decaying  wood,  etc.,  especially  where 
thick  vegetation  causes  a stagnation  of  the  air,  with  dense  shade. 
It  is  obviously  correct  then  to  cut  down  such  vegetation  imme- 
diately around  the  dajup  locality,  drain  it  and  put  it  under  culti- 
vation. If  the  rise  and  fall  of  the  water,  in  the  pond  or  marsh, 
alternately  covers  and  exposes  much  of  the  banks — i.  e.,  if  the 
banks  are  not  vertical,  or  made  so — then  the  body  of  water  must 
be  entirely  drained  off,  if  possible;  otherwise  the  injurious  de- 
compositions due  to  wet  soils  will  continue  to  go  on  and  breed, 
malaria.  It  is  found  that  winds  can  transport  malaria  some 
miles.  It  is  therefore  best  not  to  cut  down  open  forests  at  a little 
distance  from  the  damp  localities,  as  they  intercept  the  malaria 
to  a considerable  extent. 

It  is  very  often  the  case  that  dwelling-houses,  in  city  and  coun- 
try both,  are  surrounded  with  such  a dense  mass  of  .shrubbery 
(perhaps  intended  to  satisfy  the  aesthetic  taste)  as  to  cut  off  b<flh 
fresh  air  and  sunshine;  thus  rendering  the  house  and  yard  damp 
and  the  air  impure.  Such  vaults  should  be  rendered  habitable 
by  the  free  use  of  the  axe.  It  is  not  well  to  have  too  much 
shade  in  our  cities;  pure  air  and  sunshine  are  the  best  purifying 
agents  we  have.  ^It  is  a custom  (but  rarely  ‘^lonored  in  the 
breach^’)  to  deny  earnestly  and  with  many  asseverations  that 
malaria  affects  the  locality  one  lives  in.  Sad  must  be  the  con- 
dition of  that  person,  who,  even  if  he  admits  an  occasional 
malarial  fever,  cannot  point  out  another  locality  where  the  ma- 
lady is  infinitely  more  distres.sing. 

Acting  upon  this  recognized  principle,  it  is  suggested  that 
whilst  the  mountains  and  hilly  regions  hardly  ever  originate 
fever  and  ague,  that  much  of  the  remainder  of  the  State  is  sub- 
ject to  it  to  a greater  or  less  extent,  and  therefore  that  thorough 


10 


SANITARY  ENGINEERING. 


drainage  is  one  of  the  first  requisites  to  increased  healthfulness. 
Whilst  thinly  settled  districts  may  not  be  able  to  institute  pro- 
per precautions,  yet  the  larger  towns  can  drain  thp  ponds,  low 
places,  roads  and  mother  earth  generally  in  their  vicinity. 

In  the  last  column  of  the  previous  table  is  seen  the  reduction 
in  the  death-rate  from  phthisis  of  twelve  English  towns,  “This 
saving  of  life  is  ascribed  to  the  effect  of  drainage  works  in  dry- 
ing the  subsoil  of  those  places.^’ 

In  this  State,  Salisbury  may  be  given  as  an  instance  where  the 
drainage  of  a large  pond  near  the  town  has  very  largely  dimin- 
ished the  prevalence  of  malarial  fevers. 

Subsoil  Drainage. — In  the  subsoil  drainage  of  streets  and 
roads,  covered  drains,  formed  of  rock  or  tile,  should  be  used  in 
{)reference  to  open  drains.  Open  drains,  unless  the  soil  is  very 
‘tenacious,  and  can  stand  at  a steep  slope,  take  up  too  much  space. 
Besides  they  are  constantly  needing  repairs  and  often  hold  stag- 
nant water  and  decayed  filth;  so  that  in  some  countries  their 
courses  have  been  marked  by  excessive  ravages  of  cholera  over 
adjoining  districts. 

A given  tract  of  land  is  best  drained  for  agricultural  purposes 
by  stone  or  pipe  drains  of  1 to  2 inches  diameter,  running 
straight  down  the  hill-sides  (when  not  too  steep)  in  parallel  rows,. 
25  to  50  feet  apart,  and  30  to  36  intdies  below  the  surface. 
These  small  drains  discharge  into  larger  intercepting  drains,  run 
down  the  hollows;  and  these,  in  turn,  empty  into  larger  drains 
(that  may  often  be  open)  that  follow  the  courses  of  the  valleys 
and  perhaps  serve  as  the  water  channels  of  small  streams.  Such 
draining  necessarily  ensures  a deep,  mellow  soil,  that  not  only 
satisfies  the  needs  (»f  agriculture,  but  is  in  perfect  keeping  with 
the  requirements  of  health.  Towns  sliould  at  least  keep  the  sub- 
soil dry,  by  covered  drains  run  along  the  streets  and  elsewhere, 
at  sufficient  de[)ths  to  drain  the  cellars  thoroughly  and  to  [)revent 
standing  pools  of  water. 

Tile  drains  2 inches  in  diameter,  under  the  side-ditche»,  or  one 
3-inch  drain  under  the  middle  of  the  road,  is  sufficient  generally. 
An  outlet  drain  should  run  from  the  depressions  in  the  road.  A 


DRAINAGE. 


11 


drain  or  culvert  crossing  the  road  should  be  large  enough  to  pass 
2 inches  of  rain-fall  in  one  hour  when  the  drainage  area  is  small, 
1 inch  for  a valley  two  to  three  miles  long,  and  so  on. 

All  streets  and  roads  should  be  built  higher  in  the  middle 
than  at  the  sides,  and  should  have  gutters  deep  enough  to  carry 
olf  storm  waters,  unless  there  are  specially  constructed  large 
drains  for  this  purpose  (as  to  which,  and  also  the  subsoil  drain- 
age of  houses,  see  Water  Sewerage,’’  further  on). 

Complete  Drainage. — If  such  drains  (designed  to  carry  off 
all  the  rain  water,  slops  and  waste  water  that  is  not  absorbed  by 
the  ground)  are  contemplated,  regard  must  be  paid,  in  laying 
them,  to  the  future  sewerage  of  the^town,  even  if  this  is  not  car- 
ried on  at  the  same  time  as  the  drainage  system  {)ro[)er. 

The  drainage  of  large  districts,  swamp  lands,  low  lands,  etc., 
varies  so  with  the  configuration  of  the  ground  that  it  is  impossi- 
ble to  give  any  set  of  rules  that  apply  in  all  cases.  As  a rule, 
the  district  is  intersected  by  a number  of  dykes,  often  parallel, 
that  drain  into  larger  dykes  or  streams. 

Intercepting  dykes  are  often  dug  around  the  whole  area  to  be 
drained  to  prevent  the  access  of  water  from  without. 

As  an  illustration,  the  low  ‘^Landes  ” in  France  may  be  given. 
Here  260,000  acres  of  the  richest  lands  in  France  have  been 
reclaimed,  chiefly  by  cutting  open  canals  16  to  20  feet  wide,  fol- 
lowing the  natural  slope  of  the  plateau  with  a fail  of  1 to  2 per 
1,000.  Of  these  canals  1,600  miles  have  been  eompleted.  For 
75  miles  along  the  coast,  huge  sand-banks  protect  the  coun- 
try from  the  sea,  the  drainage  along  them  being  received  by  a 
large  collecting  canal  40  feet  wide.  The  works  cost  |1, 700, 000, 
about;  and  the  value  of  the  reclaimed  land  is  estimated  at  up- 
wards of  $56,000,000. 

^^The  fevers  which  formerly  ravaged  the  country  have  disap- 
peared, and  the  country  may  now  he  considered  one  of  .the  most 
healthy  in  France.” 

If  the  land  is. beneath  the  sea-level,  as  in  Holland,  then  the 
water  must  be  pumped  out  of  the  area,  the  latter  being  protected 
from  the  encroachments  of  the  sea  by  an  embankment. 


12 


SANITARY  ENGINEERING. 


Straightening  the  course  of  rivers,  likewise,  is  efficient  in 
causing  increased  scour,  a lowering  of  the  bed  and  a lessened 
liability  to  overflow. 

Ponds  are  easily  drained  by  simply  cutting  a ditch  of  the 
pro{)er  size  through  the  natural  or  artificial  embankment  sur- 
rounding them.  The  greater  the  extent  of  the  water-shed,  and 
the  greater  the  rain-fall,  and  the  imperviousness  of  the  surface, 
the  larger  of  course  is  the  ditch. 

The  so-called  ‘‘wet  weather’^  ponds,  often  on  high  ground, 
should  never  be  tolerated,  as  they  present  the  very  conditions  for 
fostering  malaria — a large  area,  alternately  wet  and  dry.* 

The  natural  division  of  a country  for  drainage  purposes  is 
into  districts  belonging  to  the  same  water-shed,  bounded,  of 
course,  by  the  ridges  and  streams.  Considerable  inconvenience 
ha’s  been  caused  in  some  thickly  settlerl  countries  by  a disregard 
of  natural  boundaries. 

The  extent  to  which  drains  exert  an  influence  on  the  ground 
on  either  side  depends  on  their  depth,  and  the  character  of  the 
soil,  whether  very  retentive  or  porous.  Their  action  is  analogous 
to  that  of  wells  given  further  on,  except  that  the  bottom  of  the 
ditch  does  not  generally  reach  the  level  of  complete  saturation 
of  the  ground  as  is  often  the  case  in  wells. 

It  is  best  not  to  open  new  ditches  from  “June  to  November’^ 
in  malarial  districts,  unless  for  house  drainage.  Cellars  should 
be  drained  by  leading  a pipe  from  below  the  bottom  of  the  cel- 
lar to  some  convenient  exit  to  the  open  air  at  a lower  level;  or 
similar  drains  may  be  laid  just  outside  of  the  building. 

It  is'plain  that  greater  attention  should  be  paid  to  drainage  in 
towns  near  our  sea-<*oast  than  in  the  hilly  regions,  as  decomposi- 
tion is  generally  greater,  due  to  increased  moisture  and  tempera- 
ture, not  forgetting  however  that  its  neglect  anywhere  must 
cause  pernicious  effects. 


^See  Kerr’s  Geology  of  N.  C.  (Introduction)  for  an  excellent  presentation 
of  the  leading  topographical  features  of  the  State,  especially  its  swamps  and 
pocosins,  as  relating  to  the  matter  in  hand. 


VENTILATION. 


13 


CHAPTER  III. 

VENTILATION. 

The  Constituents  of  the  Air. — It  has  been  found  that 
in  certain  manufactories  and  machine  shops  that  the  air  is  so 
filled  with  certain  impurities  that  30  years  is  the  maximum  age 
attained  by  the  operatives.  Such  instances  (and  they  may  be 
multiplied),  though  they  indicate  criminal  neglect  in  the  man- 
agement, are  fortunately  exceptional,  and  need  not  be  considered 
here. 

The  impurities  that  we. shall  consider  under  this  head,  as  con- 
cerning ventilation,  result  from  the  breathing  of  men  and  animals 
and  the  burning  of  gas,  oil,  etc.,  in  illumination  and  heating. 

Country  air,  wherever  analyzed,  is  found  to  contain  in  volume 
nearly  1-5  oxygen  to  4-5  nitrogen,  with  small  variable  amounts 
of  aqueous  vapor,  ammonia,  carbonic  acid  and  certain  micro- 
scopic organisms,  besides  dust,  etc. 

If  phosphorus  is  burnt  in  a bell  jar,  placed  over  water,  it  com- 
bines with  nearly  all  of  the  oxygen  in  the  confined  air,  forming 
white  fumes  of  pentoxide’’  that  are  soon  entirely 

absorbed  by  the  water,  leaving  nearly  pure  nitrogen  in  the  jar. 
The  water  rises  so  as  to  fill  about  one-fifth  of  the  original  air 
space  in  the  bell  jar,  thus  showing  that  the  substance  (oxygen) 
abstracted  is  nearly  one-fifth  by  volume  of  the  whole.  The  gas 
(nitrogen)  now  remaining  in  the  jar  is  colorless,  inodorous,  and 
does  not  support  combustion  or  animal  life.  Pure  oxygen  gas, 
(which  is  readily  obtained  separately  by  heating  mercury  oxide 
or  potassium  cholorate,  etc^),  is  likewise  colorless  and  inodorous, 
but  it  supports  combustion  readily — iron  even  burning  (oxidiz- 
ing) in  it  with  great  brilliancy. 

The  oxygen  is  the  life-giving  principle  of  the  air.  An  animal, 
however,  exposed  to  pure  oxygen  gas  is  overstimulated  to  such 
an  extent  that  it  soon  dies.  The  nitrogen,  therefore,  acts  as  a 
diluent  of  the  oxygen,  and  it  is  found  that  the  above  proportion 
of  4 to  1 cannot  be  much  varied  from  without  deleterious  con- 


14 


SANITAEY  ENGINEERING. 


sequences  ensuing.  The  oxygen  is  not  chemically  combined  with 
the  nitrogen ; it  is  simply  mixed  with  it  as  sugar  is  dissolved  in 
water — the  little  atoms  of  the  one  penetrating  the  spaces  between 
the  atoms  of  the  other  without  destroying  the  transparency  of  the 
medium. 

Dr.  Angus  Smith  has  made  a large  number  of  analyses  of  air 
in  various  parts  of  Great  Britain.  The  amount  of  oxygen  by 
volume  in  10,000  parts  of  air  are  given  for  various  localities  as 
follows : 


Mountain  air 2099  parts. 

Towns  (average) 2096 

Room  (rather  close) 2089 

Pit  of  a theatre,  11:30  P.  M 2074  “ 

Backs  of  houses  and  closets 2070 


When  air  contains  only  1850  parts  of  oxygen  to  10,000  of 
air,  it  will  not  support  the  combustion  of  a candle,  neither  will 
it  support  life  long.  The  relative  densities  of  oxygen  and  nitro- 
gen are  as  16  to  14,  so  that  an  average  composition  of  air  by 
weight  in  10,000  parts  is  oxygen  2310,  nitrogen  7690. 

The  invisible  aqueous  vapor  exists  in  the  air  at  all  times  in 
various  quantities,  often  condensed  as  visible  clouds,  dew,  etc. 
Its  amount  varies  greatly  with  the  temperature.  Thus,  one  cubic 
foot  of  air  at  90°  Fah.  can  hold  14.50  grains  of  aqueous  vapor 
as  invisible  gas;  whilst  air  at  the  freezing  point,  32°  Fah.,  can 
hold  only  2.37  grains  of  water  gas.  The  air,  in  both  cases,  is 
said  to  be  “saturated,’’  since  it  cannot  hold  any  more  water  gas, 
as  gas,  any  excess  being  precipitated  as  rain,  or  formed  into  the 
liquid  particles  constituting  fog  or  cloud  and  becoming  therefore 
visible.  • In  fact,  suppose  air,  saturated  at  90°,  to  be  cooled  down 
to  32°  suddenly:  then  12.13  grains  of  rain  will  fall  for  every 
cubic  foot  of  air,  leaving  only  a little  over  one-seventh  of  the 
original  moisture  in  the  air!  It  is  upon  this  principle  that  the 
phenomena  of  rain,  dew,  etc.,  depend. 

It  will  have  been  noticed  by  those  who  read  the  daily  reports 
given  by  the  signal  stations,  that  there  is  a column  marked 


VENTILATION. 


Id 


^‘relative  humidity.’^  This  gives  the  percentage  of  full  satura- 
tion of  the  air  at  the  time  of  observation.  Thus,  relative 
humidity  60,^’  would  indicate  that  the  air  contains  60  per  cent, 
by  weight  of  the  water  gas  it  can  hold,  without  fog  forming. 

From  Kerr’s  Geology  of  North  Carolina,  p.  87,  we  find  the 
average  yearly  humidities  of  several  places  as  follows : Wilming- 
ton 57,  Charlotte  65,  8t.  Louis  67,  London  80  and  New  Orleans 
86;  the  first  two  giving  only  the  mean  from  a little  over  one 
year’s  observations.  Whilst  in  London  fog  is  common,  on  the 
coast  of  the  Red  Sea  a cloud  never  forms,  the  dryest  air  there 
during  a simoom  containing  only  one-fifteenth  of  the  saturating 
quantity. 

Now  it  is  well  known  that  excessive  moisture  is  deleterious  to 
weak  throats,  lungs,  etc.  As  to  the  effect  of  extreme  dryness,  I 
am  not  informed,  save  that  these  little  red-hot  panting  cast-iron- 
stoves  produce  a bad  effect  on  the  air,  which  is  very  much  ame- 
liorated by  evaporating  water  in  vessels  placed  over  them.  The 
bad  effect  must  be  due  largely  to  the  drying  of  the  air.  Thus 
to  take  our  previous  example,  if  the  air  near  the  stove  is  heated 
only  from  32°  to  90°,  and  we  suppose  it.  ^‘saturated”  at  the 
lower  temperature,  then  at  the  higher  one  it  has  only  the  same 
amount  of  water  gas,  but  it  can  hold  nearly  seven  times  as  much ; 
and  if  we  suppose  it  only  half  saturated  at  32,  then  at  90  it  will 
be  nearly  as  dry  as  the  air  of  a withering  simoom,  and  at  high- 
est temperatures  much  dryer!  Such  extremes  cannot  fail  to  be 
unwholesome,  and  therefore  if  stoves  are  to  be  used,  let  them  be 
large  and  heated  as  little  as  will  give  the  necessary  warmth. 

Another  important  constituent  of  the  air  is  ammonia,  though 
it  exists  in  comparatively  minute  quantities  (about  1 in  1,000,000 
of  air);  still  it  is  mainly  from  this  ammonia  that  vegetables 
obtain  the  nitrogen  necessary  to  form  their  seeds  and  fruit.  It 
is  given  ofi*  from  urine  and  stable  manure,  unless  gypsum  is 
added  to  fix  it.  It  is  not  injurious  by  itself  in  small  quantities, 
and  need  not  be  further  considered. 

The  most  important,  by  far,  of  the  inorganic  air  constituents, 
next  to  oxygen,  is  carbonic  acid.  Its  amount  varies  within  wide 


16 


SANITARY  ENGINEERING. 


limits;  thus  in  Scotland,  mountain  air  contained  3.2  at  top  of 
mountain,  to  3.4  at  bottom,  in  10,000  volumes.  In  London  it 
varies  from  3 in  open  parks  to  3.4  on  the  Thames,  and  4 as  a 
rough  average,  on  the  streets.  In  Manchester,  the  amount  of 
6.8  to  10,000  was  reached  during  fogs,  which  is  slightly  over  the 
extreme  allowance  considered  advisable,  which  has  been  fixed  by 
some  at  6 in  10,000  volumes.  Carbonic  acid  is  formed  by  the 
chemical  combination  of  carbon  with  oxygen.  Thus  when  wood, 
coal,  oil  or  gas  is  burnt,  carbonic  acid  is  formed.  It  is  also  given 
off  by  the  decay  of  wood,  in  certain  decompositions,  and  in  the 
breathing  of  animals.  In  fact,  if  the  air  in  a jar  is  extracted 
and  then  returned  from  the  lungs  into  the  jar  again,  it  will  not 
support  the  combustion  of  a candle,  although  the  amount  of  car- 
bonic acid  expired  is  only  5 per  cent.  The  lungs  and  body  like- 
wise exhale  impurities,  about  in  proportion  to  the  amount 

of  carbonic  acid  thrown  off,  the  nose  readily  detecting  the  vitia- 
tion due  to  this  cause.  It  is  thought  by  many  that  these  organic 
impurities — fatty  matters  thrown  off  from  the  skin,  particles  of 
skin,  odors,  etc.,  from  man  and  beast — although  constituting 
only  the  one  hundred  millionth  part  of  air  in  the  country,  or 
about  the  five  millionth  part  in  crowded  cars,  is  still  the  most 
dangerous  to  man  of  the  air  constituents;  for  it  is  in  every  stage 
of  decomposition,  and  must  furnish  food  for  the  microscopical 
denizens  of  the  air,  some  of  which  no  doubt  are  scavengers,  but 
others  are  thought  by  some  to  cause  disease. 

The  Atmospheric  Germs. — It  is  well  known  now  that  fer- 
mentation and  certain  chemical  changes  are  brought  about  by 
minute  vegetable  or  animal  growths,  whose  natural  habitat  is  the 
air.  Tyndall  has  filtered  air  through  cotton  wool  to  put  next 
the  most  decomposable  substances,  and  found  that  no  change 
occurred  in  them,  whilst  common  air  caused  decomposition  or 
fermentation  to  begin.  These  experiments  pretty  conclusively 
disprove  the  theory  of  ^^spontaneous  generation.^^  Whether 
epidemic  diseases  owe  their  origin  to  ^‘atmospheric  germs”  is  not 
certainly  knowm  as  yet,  but  the  theory  is  at  least  plausible,  and 
explains  many  facts  more  fully  than  any  other  theory  generally 
known. 


VE^’TILATION. 


17 


Wl'  know  this  much,  that  sewer  gas,  even  in  the  tninutest 
quantity,  is  sometimes  fatal  (which  is  not  due  to  the  chemical 
gases  formed,  lor  the  chemist  breathes  them  every  day),  at(»ther 
times  innocuous,  especially  when  free  ventilation  has  been  secured. 
Similarly  the  discharges,  and  even  garments,  of  patients  suffering 
witli  certain  fevers  can  communicate  the  disease.  Yellow  fever, 
cholera,  small  pox,  etc.,  is  transported  in  ships  by  mere  clothing. 
These  facts,  in  connection  with  the  fact  that  certain  organisms  in 
the  air  seem  to  follow  cholera  (as  was  shown  in  Germany,  and 
the  microscope  may  reveal  the  same  thing  in  connection  with 
other  epidemics),  seem  to  point  to  the  atmospheric  germ  as  being 
connected  intimately  with  certain  diseases.  While  the  truth  is 
being  worked  out  by  scientists,  let  us  make  us(i  of  known  facts 
and  proceed  to  ^^scotch  the  snake’’,  wherever  its  presence  may  be 
reasonably  suspected. 

Vitiation  of  the  Air  by  Breathing  and  Illumina- 
tion.— It  is  found  that  a man  gives  off  somewhat  over  of  a 
cubic  foot  of  carbonic  acid  per  hour;  that  a lamp  or  two  lighted 
candles  produce  the  same  amount,  and  that  a gas  jet,  burning  3 
cubic  feet  of  gas  per  hour,  produces  as  much  carbonic  acid  per 
hour  as  two  or  three  peUple.  It  is  true  that  the  gas  gives  off  no 
organic  impurities,  but  if  not  burning  brightly  the  poisonous 
carbonic  oxide  is  always  formed. 

If  we  adopt  6 volumes  in  10,000  as  the  safe  limit  of  the 
amount  of  carbonic  acid  to  air,  then  it  follows  that  for  every 
man  or  lamp  or  two  candles  in  a room,  we  must  supply  at  least 
1,000  cubic  feet  of  pure  air  in  every  hour  to  dilute  the  ^ cubic 
foot  of  carbonic  acid  formed.  A gas  jet  will  require  two  or 
three  times  as  much  pure  air. 

But  since  the  admitted  air  contained  carbonic  acid,  we  must 
supply  more  air  to  not  exceed  the  maximum  adopted;  thus  if  the 
admitted  air  contain  three  volumes  in  10,000  of  carbonic  acid, 
we  must  admit  2,000  cubic  feet  for  every  person,  since  the  ^ of 
carbonic  acid  admitted,  added  to  the  expired  per  hour,  gives 
the  ratio  of  12  to  20,000  or  6 to  10,000  allowed. 


2 


18 


SANITARY  ENGINEERING. 


It  is  said  by  some,  that  experience  in  hospitals  shows  that 
from  2,000  to  3,000  cubic  feet  of  fresh  air  should  be  admitted 
every  hour  for  each  individual ; whilst  again  we  are  told  that 
for  a healthy  person  in  a barrack  room  1,200  cubic  feet  per  hour 
will  suffice,  and  that  the  vitiation,  tested  by  the  sense  of  smell, 
for  hospitals  is  not  perceptible  when  somewhat  less  than  the 
2,000  to  3,000  cubic  feet  are  provided. 

No  fixed  standard  has  thus  been  agreed  upon.  In  fact,  it 
doubtless  varies  with  the  climate  and  the  health  of  the  person. 
The  Laplander  can  breathe  impure  air  better  than  we,  probably 
because  the  organic  impurities  thrown  off  by  him  are  not  so 
readily  decomposed  as  in  our  warmer  air.  The  carbonic  acid 
formed  by  combustion  and  respiration  being  heavier  than  air  at 
the  same  temperature,  would  sink  to  the  floor;  but  in  conse- 
quence of  its  high  temperature,  it  first  rises  to  the  ceiling;  so 
that  as  much  as  60  to  70  parts  of  it  in  10,000  of  air  has  been 
found  at  the  top  of  an  ordinary  sized  room  in  which  two  people 
were  sitting  and  three  gas  jets  burning.  At  the  same  temperaturSy 
however,  we  should  expect  to  find  the  largest  amount  of  it  at 
low  elevations,  thus  vitiating  the  lower  strata  of  the  atmosphere, 
or  room,  very  greatly.  Fortunately,  however,  gases  have  the 
power  of  ‘diffusion so  that  a heavy  gas  will  actually  rise  to 
mix  with  a lighter  gas;  further,  it  will  pass  through  membranes 
and  thin  plates  of  stucco  to  effect  the  same  object,  so  that  the 
amount  of  carbonic  acid  is  not  generally  a function  of  the  eleva- 
tion of  a locality. 

Where  a room  has  no  flue  or  chimney  to  keep  up  a constant 
circulation,  then  openings  should  be  provided  near  the  top  of  the 
room  to  let  the  warmer  impure  gasses  out,  and  not  let  them  cool 
and  descend  again  to  vitiate  the  air  we  biTathe. 

Vitiation  by  Perspiration. — In  addition  to  the  carbonic 
acid  given  off  by  the  lungs  and  skin  of  a man,  there  is  exhaled 
a considerable  degree  of  moisture,  generally  loaded,  too,  with 
organic  matter,  which  produces  smell.  The  amount  has  been 
estimated  at  from  1.5  pounds  to  2.5  pounds  per  day  on  an  aver- 
age. A high  temperature,  or  exercise,  causes  greater  perspira- 
tion, thus  cooling  the  person  somewhat. 


VENTILATION. 


19 


The  amount  of  moisture  given  off  is  considered  by  some  in 
connection  with  the  carbonic  acid  exhaled,  to  ascertain  the  theo- 
retical amount  of  air  to  admit;  but  this  theoretical  amount  for 
most  houses  is  larger  than  healthy  persons  seem  to  require,  ac- 
cording to  certain  experience.  This  is  accounted  for  by  the  fact 
that  opening  doors  and  windows,  especially  if  they  are  kept  open 
for  some  time,  the  draft  through  cracks,  &c.,  add  very  much  to 
the  volume  of  admitted  air,  though  not  considered  in  the  com- 
putation. 

Lime  as  a Purifier. — If  a house  has  been  lately  plastered 
or  whitewashed,  the  lime  will,  at  first,  take  up  the  carbonic  acid 
with  avidity;  so  will  any  ordinary  mortar;  in  fact,  I have  seen 
artificial  stone  made  by  passing  the  products  of  combustion  of  a 
stove  (carbonic  acid  mainly)  by  a flue  into  a room  where  was 
placed  the  mortar,  moulded  into  .the  required  form.  The  lime 
of  the  mortar  changed  to  carbonate  of  lime,  which  cemented 
firmly  the  grains  of  sand  into  a hard  rock. 

It  destroys  organisms  to  whitewash.  It  would  seem,  therefore, 
that  a plastered  wall  whitewashed  was  better  than  either  the 
^^hard  finish  or  papering.  The  accumulation  of  filth  in  succes- 
sive coats  of  papering  in  old  houses  is  probably  frightful.  Most 
of  us  have  seen  the  trunks  of  trees  whitewashed.  This  seems  to 
me  a misdirected  effort  to  promote  health.  Why  should  such 
indignity  be  practiced  on  our  noblest  growths,  stopping  up  the 
pores  of  the  bark  and  probably  injuring  the  tree,  in  order  to 
remove  a little  carbonic  acid  out  of  doors,  where  it  is  not  in  ex- 
cess? 

The  Leaves  of  Plants  as  Purifiers. — The  carbonic  acid 
thrown  ofP  into  the  air  by  decomposition,  lightning,  heating  and 
the  breathing  of  animals,  is  taken  up  by  the  leaves  of  growing 
plants,  where  it  is  decomposed,  by  aid  of  the  sun’s  rays,  the  car- 
bon being  appropriated  to  help  make  woody  fibre,  &c.,  and  the 
oxygen  being  given  back  to  the  air  to  fit  it  for  respiration.  We 
cannot  imitate  this  process  in  ventilation  schemes,  but  have  to 
resort  to  heated  currents  or  to  fans  to  expel  the  foul  air  from  our 
rooms  and  leave  it  to  nature  to  carry  the  foul  air  by  the  winds  to 


20 


SANITARY  ENGINEERING. 


her  millions  of  laboratories  and  return  it  to  us  pure.  If  there 
was  no  vegetable  growth,  however,  it  has  been  computed  that  the 
breathing  of  animals  would  not  vitiate  the  air  perceptibly,  over 
the  whole  globe,  in  some  thousands  of  years. 

Limit  to  Ventilation  Schemes. — It  is  impossible  to  change 
the  air,  tdth  comfort,  in  a room,  as  often  as  the  winds  do,  out  of 
doors ; but  we  can  easily  prevent  the  air  in  the  rooms  from . be- 
coming too  impure  to  breathe.  Even  when  there  is  no  special 
attention  paid  to  ventilation,  it  is  found  that  the  hotter  inside  air 
is  going  out  continually  through  every  possible  outlet,  and  cool 
fresh  air  coming  in  to  take  its  place.  In  very  open  houses,  ven- 
tilation is  often  secured  by  the  poor  construction,  in  spite  of  the 
inmates,  but  it  is  often  at  the  sacrifice  of  comfort. 

Ventilation  by  the  Open  Fire-place. — Let  us  now  con- 
sider one  method  of  supplying  pure  air  to  a room  containing  an 
open  fire-place.  A fire  must  be  kept  brightly  burning  in  the 
fire-place,  to  heat  the  air  in  the  chimney  or  flue,  causing  a differ- 
ence of  pressure  in  the  external  and  internal  air,  so  that  the  out-* 
door  air  rushes  in  through  every  crack  and  crevice,  even  through 
the  solid  walls,  and  thus  forces  the  foul  air  up  the  chimney. 

It  is  found,  however,  by  experience,  that  the  openings  men- 
tioned are  not  generally  sufficient  to  admit  a sufficient  volume  of 
pure  air.  Hence  our  custom  is,  at  intervals,  when  headaches  or 
debility  are  experienced,  to  open  the  doors  or  windows  ^‘to  let  in 
a little  fresh  air.^’  A wise  precaution  certainly;  but  it  does  not 
meet  the  whole  case,  for  air  should  be  admitted  without  draft — 
i.  e.,  without  the  influx  of  sharply  defined  cold  currents,  which, 
as  is  well  known,  produce  colds,  with  their  attendant  evils.  The 
problem  has  been  solved,  however,  in  several  ways,  the  details 
of  which  ^re  simple  in  the  extreme. 

Thus,  if  the  lower  sash  of  the  window  is  raised  a few  inches 
and  the  opening  below  it  is  completely  closed'by  a strip  of  plank, 
there  will  still  remain  an  opening  between  the  sashes  where  they 
overlap,  through  which  the  air  will  pour,  being  necessarily 
directed  upwards.  It  thus  strikes  the  ceiling,  and  is  then  grad- 
ually diffused  through  the  room  without  draft. 


VENTILATION. 


21 


A common  expedient  of  simply  lowering  the  top  sash  allows 
the  cold  air  to  “trickle  down’’  on  our  heads.  In  the  latter  case, 
however,  a board  may  be  placed  at  an  inclination  against  the 
upper  part  of  the  sash,  so  as  to  give  the  entering  current  an  up- 
ward direction. 

Either  of  these  plans  is  liable  to  failure  when  curtains  or 
blinds  are  used.  So  that  a more  generally  applicable  method 
would  consist  in  boring  holes  through  the  upper  part  of  the 
doors  or  walls,  and  giving  the  entering  air  an  upward  direction 
by  means  of  inclined  planes  of  some  kind;  or  tubes  of  wood  or 
iron  may  be  passed  through  the  walls  and  turned  directly  up- 
wards on  entering.  They  should  extend  to  at  least  7 feet  above 
the  floor. 

The  air  in  all  cases  should  be  drawn  directly  from  out-doors, 
and  not  from  passages  or  other  rooms.  The  openings,  moreover, 
should  admit  of  being  partially  or  entirely  closed  on  very  stormy 
.and  windy  days.  All  of  the  above  plans  hav^e  been  tried  in 
dwellings,  club-rooms,  etc.,  with  complete  success. 

The  proper  size  of  tube  or  opening  to  use  must  be  determined 
by  experience.  Two  tubes,  of  two  inches  diameter  each,  may  be 
tried  for  an  average- sized  room  for  two  persons.  It  is  stated 
fhat  “two  square  tubes,  5x5  inches,  will  keep  a good-sized  club- 
room  fresh” 

• . . . ' . 

Now,  this  method  of  ventilation  is  dependent  upon  a fire  being 
maintained  at  the  lower  level  of  the  room  to  cause  the  currents 
to  enter  with  sufficient  velocity.  The  system  fails  in  summer; 
when,  however,  we  do  not  object  to  the  draft  caused  by  opening 
the.doors  and  windows. 

Known  Properties  of  Air.— The  mathematics  of  this 
branch  of  the  subject  (which  is  not  given,  as  it  seems  out  of 
place  here)  depends  upon  certain  known  properties  of  air  which 
may  be  briefly  mentioned.  Thus  12.4  cubic  feet  of  air  weighs 
1 pound,  when  at  a temperature  of  32°  F.,  the  barometric  height 
being  about  30  inches,  the  average  pressure  at  the  sea-level. 

Since  air  is  compressible  (its  volume  varying  inversely  as  the 
pressure),  it  follows  that  as  we  ascend,  the  weight  of  the  same 


22 


SANITARY  ENGINEERING. 


volume  of  air  becomes  less,  since  there  is  less  air  above  us  than 
before,  so  that  the  same  weight  of  air  is  not  compressed  into  so 
small  a place. 

Air  likewise  expands  or  contracts  part  of  its  volume  for 
each  degree  Fahrenheit  above  or  below  the  freezing  point,  the 
pressure  remaining  the  same;  so  that  491  volumes  of  air  at  32° 
becomes  499  volumes  at  40°,  509  at  50°,  519  at  60°,  529  at  70°, 
539  at  80°  and  549  volumes  at  90°;  whilst  the  491  volumes  at 
32°  F.  become  479  at  20°,  469  at  10°  and  459  at  0°  Fahrenheit. 

Again,  it  is  found  that  one  pound  of  air  can  be  raised  1°  F. 
by  the  same  amount  of  heat  that  will  raise  0.2374  lbs.  of  water 
through  one  degree,  the  air  being  subjected  to  constant  pressure. 

From  such  data,  in  connection  with  the  heat  afforded  by  dif- 
ferent fuels,  and  the  laws  affecting  the  flow  of  gases,  we  are  ena- 
bled to  compute  the  velocity  of  the  air  flowing  out  of  the  chim- 
ney, which  is  thus  a measure  of  the  inflow  of  the  fresh  air. 
Suffice  it  to  say,  that  the  higher  the  chimney  or  flue  the  stronger 
the  draught,  as  thereby  the  difference  of  weights  of  the  heated 
air  in  the  chimney  and  a similar  column  outside  the  chimney  is 
greater. 

Ventilation  by  Gas  Jets. — In  theatres  and  closed  halls, 
a series  of  gas  jets  may  be  used  to  create  a current,  the  heated 
air  passing  out-doors  through  flues  placed  directly  over  the  gas 
jets. 

It  is  stated  that  this  plan  has  met  with  great  success  in  two 
churches  in  New  York,  the  size  of  one  of  them  (Dr.  ScuddeFs 
church)  being  150x100,  of  the  other  (Dr.  Hepworth’s)  125x125; 
the  first  seating  2,200  and  the  second  2,400.  There  were  four- 
teen to  twenty  twelve-inch  round  tin  pipes,  carried  up  in  walls 
from  near  the  floor  to  and  above  the  roof.  In  each  of  these  tubes 
was  placed  three  gas-burners,  just  above  the  registers  that  admit 
air  from  the  outside.  On  simply  heating  some  of  these  gas  jets, 
the  registers  being  opened  the  proper  amount,  there  is  caused  a 
quick  exhaust,  under  complete  control,  and  an  inflow  of  pure 
fresh  air.  There  is  an  opening  in  the  centre  of  the  ceiling  of 
the  auditorium  into  an  octagon-shaped  shaft  eleven  feet  in  diam- 


VENTILATION. 


23 


eter  iu  onfe  church,  sixteen  in  the  other,  extending  alxwe  roof, 
containing  sashes  and  outlets  to  the  outer  air.  -Gas  jets  are 
placed  under  tubes  in  these  shafts  to  increase  the  current.  At 
other  {)arts  of  the  ceiling  are  similar  shafts,  etc.  The  numerous 
gas  jets  produce  such  a current  that,  in  warm  weather , the  entire 
air  of  the  church  can  be  changed  every  five  minutes.  The 
churches  are  heated  by  hot-air  furnaces  or  steam  coils.  (See 
‘^Plumber  and  Sanitary  Engineer,’’  March,  1879). 

Ventilation  by  Fans.— Still  another  method  of  ventila- 
tion is  by  pumps  and  fans.  Most  generally,  air  is  drawn  from 
without  by  fans  located  in  the  basement,  and  is  propelled  along 
ducts — -.over  steam  pipes  or  furnaces,  if  it  is  to  be  heated — to 
openiijgs  into  the  various  halls  and  rooms,  from  whence  it  escapes 
by  suitable  openings,  generally  placed  in  the  roof.  The  air  is 
often  drawn  from  near  the  ground,  but  it  is  best,  especially  in 
densely  populated  cities,  to  draw  the  fresh  air  from  a point  100 
to  200  feet  above  the  ground  down  vertical  shafts.  In  Paris 
the  air  is  drawn  down  a shaft  180  feet  in  height  to  supply  the 
Assembly-room.  (See  Appendix  III,  for  a description  of  the 
ventilation  of  the  New  York  Lunatic  Asylum). 

Good  Effects  of  Ventilation. — It  is  evicieut  how  im- 
portant a factor  of  healtli  ventilation  is  in  crowded  school-rooms; 
in  fact,  in  all  places  where  crowds  may  congregate  and  speedily 
vitiate  the  air.  The  bad  effects  are  everywhere  admitted.  The 
^ood  effects  of  the  systems  proposed  have  been  proved  by  mor- 
tuary statistics,  especially  in  school-houses  and  hospitals.  In  a 
Dublin  hos[)ital,  in  1783,  for  twenty-five  years  when  the  venti- 
lation was  bad,  3,000  out  of  18,000  children,  born  there,  died 
within  the  first  fortnight  of  their  birth.  With  better  ventilation 
in  the  succeeding  twenty-eight  years,  550  died  out  of  every 
15,072. 

The  report  of  1861  states  that  further  improvements  in  ven- 
tilation have  been  made,  and  deaths  from  the  nine-day  fits,” 
which  carried  off  most  of  the  infants,  was  then  almost  unknown. 

The  records  concerning  ventilation  in  connection  with  lung 
diseases  is  equally  striking.  Such  diseases  thrive  in  cities  where 


24 


SANITARY  ENGINEERING. 


the  smoke  resulting  from  the  burning  of  coal  is  charged  with 
impurities,  such  as  “hydrocarbons,  sulphide  of  ammonium, ‘car- 
bonic oxide,  and  probably  very  minute  quantities  of  arsenic.’’ 
Even  now  the  cry  is  going  up  from  London  for  a purification  of 
its  atmos})here  from  smoke.  This  evil  we  do  not  suffer  much 
from  in  North  Carolina,  the  population  being  scattered  and  the 
cities  small.  But  we  need  a thorough  inspection  of  public  build- 
ings with  a view  to  proper  ventilation. 

When  it  is  known  that  30  parts  of  carbonic  acid  to  10,000  of 
air  is  often  found  in  theatres  and  public  hails,  which  is  five  times 
the  admissible  amount,  it  will  be  admitted  that  reform  is  needed. 

Cubic  Space  Allowed. — The  amomit  of  space  per  head 
allowed  in  the  roQm  by  various  autho7'ities,  varies  from  300  to 
1,000  cubic  feet,  the  amount  being  smaller  when  the  room  is 
only  occasionally  filled  with  its  maximum  number. 

It  is  true  that  the  air  can  be  changed  in  a small  room  more 
frequently  than  in  a large  one  to  maintain  the  proper  degree  of 
purity  or  rather  impurity,  but  the  increased  draught  may  be 
objectional)le.  The  amount  of  space  actwdly  given  per  head  in 
various  school-houses  varies  from  70  to  100  to  200  cubic  feet. 
The  effect  is  that  12  parts  of  carbonic  acid  in  10,000  (double 
the  admissible  amount)  is  common,  and  even  20  and  50  parts  are 
not  unknown..  The  effect  upon  both  teacher  and  pupils  is  of 
course,  headaches,  listlessness  and  debility. 

Lighting.— The  proper  lighting  of  school-rooms  is  as  ut*ces- 
sary  as  ventilation.  The  light  should  come  from  behind  th^ 
pupil  on  to  the  book  or  blackboard,  when  possible,  and  the  win- 
dows should  be  high,  as  most  of  the  available  light  comes  from 
above  the  level  of  our  heads.  Lighting  directly  from  the  top  is 
probably  the  most  efficient  means  of  all  where  practicable.  The 
light  should  come  mainly  from  one  side — the  side  o})f)Osite  the 
blackboards— and  the  pupils  should  sit  with  their  backs  to  it. 
The  desks  should  be  at  such  heights  that  the  book  or  paper,  &c., 
shall  not  be  too  near  the  eyes,  so  that  the  tendency  to  near-sight- 
edness may  be  prevented.  This  detect  is  becoming  alarmingly 
{irevalent,  and  tlie  teacher  should  insist  upon  the  pupil  reading 


V^ENTILATION. 


25 


with  the  book  at  the  proper  distance  to  suit  his  vision,  at  all 
times. 

Useful  Hints. — Finally,  let  it  be  impressed  upon  all  that 
the  sense  of  smell  when  coming  from  out-doors  into  a room  should 
warn  us  when  our  rooms  are  foul,  and  that  .doors  and  windows 
should  be  opened  when  convenient,  and  articles  of  clothing  and 
bedding  should  be  aired  frequently  to  purify  them. 

Also  let  it  be  remembered  that  even  brick  walls  can  transmit 
gases.  “Pettenkofer  got  2,650  to  3,320  cubic  feet  of  air  through 
the  brick  walls  and  crannies  of  his- room,  when  the  difference  of 
temperature  inside  and  outside  was  34°  F.  When  all  the  cran- 
nies had  been  carefully  stopped  up,  1,000  cubic  feet  per  hour  still 
came  through  the  walls.’’  Therefore  never  aPow  filth  about  any 
room  or  cellar  of  the  house,  nor  against  the  outside  walls,  for 
such  filth  will  contaminate  the  air  that  comes  into  the  room,  and 
has  been  found  to  cause  sickness.  If  the  house  is  liable  to  such 
contagion  from  adjoining  buildings,  endeavor  to  make  it  as  air- 
tight as  possible,  after  providing  for  the  admittance  of  the  pur- 
est air  that  can  be  obtained  through  proper  openings.  The  floors 
of  all  houses  should  be  as  tight  as  possible. 

Heating. — Intimately  connected  with  ventilation  is  heating; 
in  fact  the  two  have  generally  to  be  considered  together.  In 
cold  weather  we  require  more  heat  than  our  bodies  generate  to 
make  up  for  the  loss  by  radiation;  at  the  same  time  we  need 
fresh  air  to  breathe. 

How  admirably  are  these  two  conditions  realized  around  a 
good  camp-fire,  on  a still,  cool  night!  The  active  worker  has 
just  enjoyed  his  hearty  meal,  as  only  a worker  can,  and  with  feet 
stretched  to  the  fire — that  heats  him  by  direct  radiation — and 
body  well  clad,  inspires  the  cool,  fresh  air  o'f  the  country  that 
invigorates  body  and  mind. 

Cool  air  to  breathe  is  as  refreshing  as  cool  water  to  drink, 
whilst  air  too  warm  may  be  compared  with  tepid  water  in  its 
effects.  This  fact  is  universally  admitted,  and  yet  it  has  got  to 
be  the  fashion,  at  the  North  especially,  to  heat  houses  by  puffs  of 
hot  air  from  furnaces  that  would  seem  more  properly  in  keeping 


26 


SANITAKY  ENGINEERING. 


with  a dryiijg-house.  Let  us  understand  clearly  the  physical 
differences  in  the  various  methods  of  heating,  and  we  can  then 
form  a more  intelligent  judgment  as  to  the  merits  or  demerits  of 
each  particular  device. 

The  open  fire  heats  solid  bodies  in  front  of  it,  by  direct 
radiation  of  heat  rays,  which  pass  through  the  intervening  air 
with  scarcely  any  loss.  Tyndall  has  shown  that  air,  consisting 
simply  of  oxygen  and  nitrogen,  intercepts  but  an  extremely 
small  number  of  heat  rays  passing  through  it.  The  aqueous 
vapor,  found  in  all  air,  intercepts  30  to  100  times  the  heat  that 
pure  air  does.  Carbonic  acid,  perfumes,  etc.,  increase  the  absorp- 
tion of  heat  by  air.  The  water  gas  in  the  atmosphere,  although 
constituting  only,  say  J [)er  cent,  of  it,  yet  intercepts  nearly  all 
the  heat  rays  of  the  sun  that  do  not  reach  the  earth ; and  again 
prevents  their  too  rapid  radiation  at  night  from  the  earth.  As 
Tyndall  says,  “Aqueous  vapor  is  a blanket,  more  necessary  to 
the  vegetable  life  of  England  than  clothing  is  to  man.’’  The 
amount  of  heat,  however,  intercepted  by  the  air  between  the  fire 
of  a room  and  solid  objects  in  front  of  it,  although  small,  yet 
does  increase  the  temperature  of  the  air  somewhat,  though  it  is 
usually-  neglected  altogether.  The  air  of  the  room  is  mainly 
warmed  by  convection, from  coming  in  contact  with  the  solid 
objects  that  have  a higher  temperature;  the  air  next’ the  solid 
body  being  heated  first,  then  rises,  to  be  replaced  by  other  air, 
which  operation  is  repeated  indefinitely,  or  until  the  whole  mass 
is  heated  to  the  same  temperature. 

There  is  thus  a continual  circulation  of  the’  air  in  a room 
heated  by  an  open  fire-place,  and  generally  an  efficient  draught 
to  keep  the  air  from  being  too  much  fouled. 

If  the  room  is  heated  by  steam  or  hot-water  pipes,  the 
case  is  different.  The  direct  radiation  is  small,  as  any  one  can 
test  by  trying  to  warm  his  feet  at  the  pipes  without  actual  con- 
tact. The  warming  is  mainly  eff'ected,  as  in  the  case  of  stoves 
(not  overheated)  or  hot-air  furnaces,  by  the  air  being 
warmed,  by  the  heated  pipes,  stoves  or  furnaces,  by  convection, 
and  this  air  by  its  circulation  heats  the  room  and  its  occupants. 


VENTIJ.ATION. 


27 


The  aiv  is  thus  warmer  than  the  furniture  in  the  room  ; whereas 
in  heating  by  the  open  fire-place,  the  furniture,  etc.,  is  often 
warmer  than  the  air.  A person  in  the  room  would  thus  be  con- 
tinually radiating  heat,  unless  the  air  was  too  warm  for  comfort. 
In  addition  to  the  objection  to  the  warm  air_per  se,  it  has  been 
previously  explained  that  heating  air  causes  it  to  become  tpo  dry; 
so  that  whilst  the  ^‘relative  humidity’’  out  of  doors  may  be  80, 
in-doors  it  may  be  much  less — a disproportion  that  cannot  be 
conducive  to  health.  In  fact,  as  a writer  humorously  remarks, 
such  drying-houses  ‘^are  drying  the  very  flesh  off  the  bones  of 
the  Americans.” 

Still,  in  large  buildings  it  is  generally  impracticable  to  heat 
by  direct  radiation,  and  the  inmates  have  to  submit  to  be  dried. 
Again  it  is  stated  that  the  rigor  of  the  Northeru  climate  requires 
that  the  air,  even  in  dwelling-houses,  be  heated  somewhat  before 
being  admitted.  If  so,  then  it  is  still  practicable  to  heat  it  only 
to  50°  or  70°  F.,  and  supplement  with  the  open  fire-place. 

Summary  of  Modes  of  Heating  in  the  Order  of  Merit. 
— We  shall  conclude  this  popular  exposition  of  the  subject  by  a 
condensed  summary  of  the  various  modes  of  heating  in  vogue, 
in  the  same  order  of  merit  as  that  given  by  Prof.  Fleming  Jen- 
kin,  in  “Healthy  Plouses”  (Harper’s  Half  Hour  Series),  a book 
that  every  one  should  have. 

The  open  fire-place  is  best,  although  most  expensive,  as  it 
heats  by  radiation^  and  secures  ventilation. 

Next  follow,  in  the  order  of  descending  merit,  hot-water  pipes, 
porcelain  stoves,  hot-air  pipes,  cast-iron  stoves,  and  last  and 
worst,  gas-stoves  with  no  chimney.  These  pipes  and  stoves  heat 
largely  by  convection — i.  e.,  by  heating  the  air  next  to  them, 
which  rises  and  is  diflused  through  the  room,  the  cold  air  taking 
its  place  to  be  in  turn  heated,  &c. 

Iron  stoves,  especially  when  overheated,  emit  a bad  smell, 
supposed  to  arise  from  the  charring  or  decomposition  of  organic 
substances  in  the  air  by  their  contact  with  the  heated  sides  of  the 
stove  and  pipe.  Moreover,  if  the  stove  is  red-hot,  the  poisonous 
carbonic  oxide  and  other  gases  will  pass  through  the  red-hot  iron 


28 


SANITAEY  ENGINEERING. 


and  thus  enter  the  room.  The  air  is  charred  and  dried  too  much 
by  iron  stoves.  The  porcelain  are  far  preferable.  Hot-air  pipes 
are  better,  and  moreover  distribute  the  heat  more  uniformly; 
though  if  the  furnace  becomes  red-hot,  poisonous  carbonic  oxide 
will  pass  into  the  pipes.  Some  describe  the  ^‘hot  air”  as  having 
the  ^Mife  taken  out  of  it.”  Hot-water  pipes  are  better  than  hot- 
air pipes;  the  air  is  not  overheated,  and  a uniform  temperature 
is  preserved  for  a long  time.  It  is  much  used  in  hot-houses, 
baths,  drying-rooms,  etc. 

Exits  must  be  provided  for  the  foul  air  where  the  hot-air  sys- 
tem, the  water-pipes  or  the  gas-stoves  are  used.  For  comfort 
and  cheerfulness,  no  device  can  e(^ual  the  open  fire-place,  fed 
with  coal,  or  oak  and  hickory  wood,  not  ignoring  either  the 
historic  pine. 

The  fresh  air  then  comes  in  through  the  walls,  tubes,  etc., 
cold,  with  plenty  of  oxygen  and  perhaps  ozone  in  it,  and  is  grad- 
ually diffused  through  the  room  as  it  becomes  heated,  to  give  up 
the  proper  amount  of  oxygen  required  for  respiration  and  com- 
bustion. What  excuse  can  there  be  for  close  rooms,  that  breed 
debility  of  various  kinds,  when  pure,  fresh  air  can  be  obtained 
by  us  at  such  a small  cost? 


CHAPTER  IV. 

WATER  SUPPLY. 

All  of  our  supplies  of  water  are  derived  from  rain-fall,  part  of 
this  rain-fall  evaporating  again,  part  running  off  into  the  streams 
and  thence  into  the  ocean  to  be  again  distilled  and  sent  back  to 
us  as  clouds  and  rain,  and  part  sinking  into  the  earth  and  form- 
ing the  small  subterranean  streams  which  furnish  the  water  of 
our  springs  and  wells.  In  running  over  or  through  the  ground, 
this  water  takes  up  such  salts  as  it  meets  that  are  soluble.  Some 
of  these,  together  with  the  air  and  carbonic  acid  dissolved,  giv- 
ing the  pleasant  taste  to  our  usual  potable  waters. 


WATER  SUPPLY. 


29 


Other  salts  and  gases,  derived  from  decaying  .organic  matter — 
dead  bodies,  manure,  filth,  etc. — are  harmful  in  the  highest 
degree,  and  have  bred  mischief  and  death  in  innumerable  cases. 

The  rain  as  it  leaves  the  clouds  is  pure  water  generally;  but 
in  falling  to  the  ground,  it  not  only  carries  with  it  mechanically 
much  organic  matter  and  dust  that  is  floating  in  the  air,  but  it 
dissolves  various  gases,  as  oxygen,  nitrogen,  carbonic  acid  and 
ammonia  (the  usual  constituents  of  the  atmosphere),  besides  nitric 
acid  (often  formed  in  the  air  by  the  lightning’s  flash),  and  in  the 
vicinity  of  manufacturing  towns,  the  gases  evolved  in  the  pro- 
cesses used  in  the  particular  manufacture.  Water  readily  dis- 
solves certain  gases.  On  simply  shaking  it  up  with  air,  the  lat- 
ter is  readily  dissolved.  This  principle  is  made  use  of  in  aerat- 
ing the  pure  water,  that  has  been  distilled  from  the  salt  water 
of  the  ocean,  on  board  ships,  thus  making  it  drinkable. 

The  amount  of  oxygen,  nitrogen,  carbonic  acid  and  ammonia 
commonly  found  in  waters  is  small,  particularly  the  ammonia; 
which  last,  it  may  be  observed,  water  can  dissolve  in  large  quan- 
tities. All  of  these  gases  are  easily  expelled  by  simply  boiling 
the  water. 

Rain  water  generally  contains  far  less  organic  matter  than 
river  water.  River  waters,  though,  differ  greatly  in  the  amount 
and  character  of  the  matter,  in  solution  and  suspension,  as  re- 
gards potability.  Thus,  if  water  drains  over  an  impervious  stra- 
tum, as  a granitic  formation,  the  water  is  apt  to  be  soft,  and  to 
contain  but  little  solid  matter  in  solution.  Some  waters  of  this 
character  contain  only  from  three  to  five  grains  of  solid  matter 
to  the  gallon ; they  possess  a high  solvent  power  on  lead  ^and 
iron  pipes,  but  are  otherwise  of  the  best  character. 

Where  the  rocks  consist  largely  of  carbonates  of  lime  or  mag- 
nesia, the  waters  are  apt  to  be  hard,  their  action  on  lead  and  iron 
pipes  is  small,  and  they  require  a greater  expenditure  of  soap  in 
washing,  but  are  not  otherwise  objectionable,  unless  the  carbon- 
ates are  greatly  in  excess. 

It  is  stated  that  the  health  and  physique  of  hard  water  dis- 
tricts is  better  than  in  soft  water  districts;  the  water  furnishing 
an  abundance  of  material  needed  in  the  formation  of  the  bones. 


30 


SANITARY  ENGINEERING. 


Each  ^‘degree  of  hardness  (i.  e.,  each  grain  of  chalk  or  sul- 
phate of  lime,  dissolved  in  a gallon  of  water)  will  entail,  how- 
ever, the  additional  use  of  two-and-a-half  ounces  of  soap  for 
every  100  gallons  of  water;  so  that  it  is  well  to  get  rid  of  the 
carbonates  in  solution,  if  possible.  This  may  be  partially  effected 
in  two  ways;  either  by  boiling  the  water,  or  by  adding  milk  of 
lime.  Both  methods  depend  on  the  fact  that  water  can  dissolve 
only  two  grains  per  gallon  of  carbonate  of  lime,  unless  it  con- 
tains carbonic  acid  in  solution,  when  it  can  dissolve  very  much 
more* 

Boiling  expels  this  acid ; thus  reducing  the  amount  of  carbon- 
ate of  lime  in  the  water  in  solution  to,  at  most,  two  grains  per 
gallon.  By  the  second,  called  Clarke’s  process,”  the  added 
lime-water  combines  chemically  with  all  the  free  carbonic  acid, 
forming  carbonate  of  lime,  which  thus  settles  to  the  bottom, 
together  with  much  of  the  original  carbonate  of  lime,  leaving 
only  about  two  grains  per  gallon  still  in  solution  of  carbonate  of 
lime. 

The  milk  of  lime  is  made  by  shaking  up  a small  quantity  of 
quick  lime  in  water. 

Permanent  hardness  of  water  is  caused  by  the  presence  of  sul- 
phates of  lime  and  magnesia.  Neither  boiling  nor  Clarke’s  pro- 
cess can  soften  such  water. 

Wells  and  Sp^iings. — Where  wells  or  springs  are  used  as 
the  source  of  water  supply,  great  care  should  be  taken  that  the 
surface  in  their  vicinity  be  kept  free  from  organic  matter,  which 
by  oxidation  and  putrefaction  readily  forms  soluble  nitrates,  am- 
monia and  chlorides. 

Such  waters  are  often  clear,  pleasant  to  the  taste,  sparkling  from 
the  excess 'of  carbonic  acid  and  cool  from  the  effects  of  the  nitrates. 
Hence  the  senses  cannot  be  relied  on,  without  the  aid  of  a chem- 
ical and  microscopical  analysis  to  decide  whether  our  well  water 
is  fit  to  drink.  Even  when  all  filth,  slops,  etc.,  are  removed  to 
a distance,  we  can  only  infer  that  there  is  no  probable  contamina- 
tion. 


WATER  SUPPLY. 


31 


The  geological  structure — stratification,  faults,  character  of  the 
earth,  etc. — should  be  studied  in  this  connection.  Thus  it  was 
found  in  a certain  locality  that  wells  very  near  a grave-yard  gave 
good  water,  whereas  wells  on  the  opposite  side,  several  hundred 
yards  off,  in  the  direction  of  the  dip  of  the  strata,  were  polluted 
to  a dangerous  extent.  The  explanation  is  simply  that  water 
has  a tendency  to  fiow  along  the  planes  of  stratification,  where 
the  strata  are  well  defined. 

Numerous  cases  of  fever,  cholera,  &c.,  have  been  traced  to  bad 
water;  localities  with  wells  situated  on  the  subterranean  current 
that  flowed  past  the  diseased  refuse,  cess-pool,  etc.,  being  attacked, 
whilst  neighboring  localities  were  free  from  the  epidemic.  It  is 
needless  to  specify  particular  instances.  Let  no  wells  be  placed 
where  kitchen  refuse,  slops,  manure  or  any  kind  of  fecal  matter 
can  drain  into  them.  Where  no  stratification,  exists,  then,  if 
possible,  place  the  well  two  or  three  times  its  depth  from  any 
offending  matter.  A well  can  just  as  properly  be  dug  next  to 
the  house  as  elsewhere,  provided  slops  and  kitchen  refuse  are 
emptied  some  distance  from  it.  In  one  instance  soapy  water 
was  found  by  analysis  in  one  well,  whose  sparkling  waters  would 
never  have  suggested  it.  The  whole  of  the  slops  of  the  estab- 
lishment were  thrown  w'here  they  drained  directly  into  the  well. 

It  must  be  carefully  borne  in  mind  that  the  well  is  the  point 
of  least  resistance  to  the  numerous  little  streams  entering  it  and 
that  it  may  induce  a flow  from  a considerable  extent  of  the  sur- 
rounding earth.  Chemical  analysis  o^n  alone  show  if  some  of 
these  little  streams  have  been  polluted;  in  fact,  whether  a well 
is  the  drainage  receptacle  of  the  filth  on  the  surface  or  of  the 
rotten  cess-pool — the  disgrace  of  any  land  where  it  is  found. 

It  is  not  intended  to  convey  the  idea  that,  before  wells  are  dug, 
the  underground  water  is  necessarily*  flowing  in  little  streams. 
On  the  contrary,  it  is  generally  otherwise,  particularly  in  very 
absorptive  strata.  Very  hard  rocks  of  course,  hold  but  little 
water,  except  in  the  crevices,  whilst  very  porous  and  absorptive 
strata,  as  the  London  chalk,  are  fully  saturated  with  water  from 
near  the  surface  downwards,  and  only  need  tapping  to  afford  it 
in  large  quantities. 


32 


SANITARY  ENGINEERING. 


The  water  thus  coutaiued  in  the  ground  is  known  as  the  “soil^^  ’ 
or  ‘Aground’’  water.  Where  the  earth  is  porous,  absorptive  and 
uniform  in  character,  much  more  of  the  rain-water  passes  into 
the  ground  to  flow  oflP  along  subterranean  channels  to  some  out- 
let, to  appear  at  the  surface  again  as  springs,  or  to  be  pumped 
out  of  wells — than  where  the  surface  is  more  impervious. 

The  imaginary  line  connecting  the  water-level  of  springs  and 
wells  (when  not  used)  is  called  “the  line  of  saturation.’’  It  has 
been  found  that  in  uniform  earth  this  line  of  saturation  generally 
rises  with  the  ground,  so  that  generally  as  we  recede  from  the. 
sea-coast,  or  a stream,  the  Water-level  of  the  well  rises,  whilst  its 
depth  beneath  the  surface  increases.  This  rule  is  often  true  even 
when  there  is  a want  of  uniformity  in  the  strata  or  in  the  con- 
figuration of  the  ground,  though  so  much  depends  upon  the 
inclination  the  beds  have,  and  their  relative  permeability,  that  it 
is  impossible  to  lay  down  any  precise  rules  as  to  where  water 
may  be  struck  in  any  but  the  simplest  cases. 

This  is  still  more  evident  if  the  rocks  are  contorted,  fissured 
or  faulted. 

Some  special  cases  may  be  given  however.  Thus  if  a porous 
stratum  overlies  an  impervious  one,  the  water  descends  through 
the  former  until  it  reaches  the  latter.  Now  as  the  lower  stratum 
ij  level,  or  slopes  towards  its  outcrops,  or  is  depressed  in  the 
middle,  the  water  which  soaks  through  the  porous  stratum  will 
eventually  appear  in  the  form  of  springs  near  the  upper  line  of 
the  outcrop  of  the  lower  stratum,  or  be  mostly  stored  in  the 
depression  mentioned  of  this  stratum.  Unless  the  porous  stratum 
is  very  shallow,  wells  may  be  dug  in  it,  especially  in  the  last  case 
mentioned,  with  the  expectation  of  getting  a good  supply  of 
water. 

Where  the  porous  stratum  is  covered  by  an  impervious  one,  it 
holds  less  water  than  in  the  previous  case,  for  it  now  receives  no 
.water  except  along  its  outcrop. 

Where  such  porous  strata,  however,  are  of  great  extent  and 
have  a considerable  outcrop  (it  may  be  in  remote  districts)  a good 
supply  of  water  may  be  expected. 


WATER  SUPPLY. 


33 


111  the  latter  case,  if  the  porous  strariiin  is  again  underlaid 
with  an  impervious  one  which  is  depressed  in  the  middle,  large 
quantities  of  water  will  collect  in  this  basin  under  consid  rable 
hydrostratatic  pressure.  If  this  pressure  is  sufficient  to  send 
water  to  the  surface  through  a well-hole,  the  result  is  an  artesian 
well,  which  wells  are  much  resorted  to  in  some  countries. 

In  this  State  we  need  have  no  fears  of  a water  famine  if  the 
various  sources  are  utilized.  In  the  Quarternary  sand  of  the 
eastern  portion  of  the  State,  wells  only  15  feet  deep  are  common, 
though  the  underlying  Tertiary  marls  and  older  rocks  may  cause 
exceptional  features.  In  the  middle  and  western  portion  of  the 
State,  the  rocks  are  sandstones,  slates  and  various  crystalline 
rocks,  which  are  often  fissured,  faulted,  contorted  or  intersected 
by  trap-dykes;  thus  causing  abnormal  features:  still,  as  the  dip, 
except  in  the  sandstone  formation,  is  often  considerable,  there  is 
not  generally  much  difficulty  in  finding  water  on  digging  for  it; 
so  that  the  diviner’^  with  his  witch  hazel  twig  generally  finds 
his  predictions  verified.  Perhaps  it  would  be  the  same  if  he  did 
not  invoke  its  mysterious  powers  to  assist  him!  In  the  older 
rocks,  the  water  often  collects  in  fissures.  Instances  are  known 
where  pumping  from  one  well  affects  a remote  one;  whilst,  on 
the  other  hand,  owing  to  faults,  dykes,  change  of  dip,  etc.,  wells 
very  near  together  seem  to  have  no  connection. 

As  a rule,  the  wells  are  deeper  in  the  older  rocks ; for,  as  the 
latter  are  more  impervious  than  the  sands  of  the  later  formations, 
less  water  is  absorbed  by  them — more  running  off  into  the 
streams — therefore  we  should  naturally  expect  to  go  deeper  for  a 
constant  supply.  Other  things  being  equal,  the  deeper  the  well 
the  purer  the  water,  as  it  has  filtered  through  a greater  extent  of 
earth. 

The  earth  is  thus  a vast  sponge,  ready  to  afford  water  when 
tapped,  that  is  generally  of  a better  quality  too  than  lake  or  river- 
water  in  the  vicinity. 

Prof.  Nichols  (see  “Filtration  of  Potable  Waters’’)  has  ob- 
served, that  even  when  the  well  is  situated  near  a stream,  that 
“ the  water  is  generally  clear  and  colorless,  of  a nearly  uniform 
3 


34 


SANITARY  ENGINEERING. 


temperature,  and  differs  in  chemical  character  from  that  of  neigh- 
boring streams  or  ponds,  generally  being  somewhat  harder.^’ 

On  lowering  the  level  of  the  water  in  such  basins  by  pumping 
or  otherwise,  the  ground-water  level  is  lowered  next  the  basin  to 
the  same  extent;  but  it  is  found  that  as  we  proceed  from  the 
well  or  basin,  that  this  level  is  lowered  less  and  less,  until  we 
reach  a point  which  is  not  affected  when  the  level  of  the  water 
in  the  basin  is  kept  at  a certain  minimum  height,  the  friction 
and  capillarity  balancing  gravity  here;  supposing  always  the 
rain-fall  not  subject  to  much  variation.  In  case  of  drought,  of 
course  the  whole  ground-water  level  would  be  lowered. 

As  an  illustration  of  the  above  principle,  it  was  found  on  the 
Elbe,  that  when  the  water  in  a well,  dug  in  an  alluvial  deposit, 
was  kept  constantly  8.2  feet  below  its  normal  level,  that  the 
height  of  the  ground-water  was  affected  in  every  direction  for 
200  feet  only. 

Large  basins,  near  streams,  are  often  used  as  the  source  of 
water  supply  of  whole  towns.  Now  it  is  evident  that  if  the 
water-level  is  lowered  in  such  a basin  that  since  the  water- 
level  in  the  intervening  bank  is  lowered,  that  the  river-water 
will  have  a tendency  to  flow  tow^ards  the  well  to  make  up 
the  deficiency,  unless  the  bottom  and  sides  of  the  river  have 
become  coated  with  clay  to  such  an  extent  as  to  be  impervious, 
which  is  very  apt  to  be  the  case  unless  the  stream  is  very  clear, 
or  has  a rapid  current.  Known  examples  seem  to  show  little  or 
no  contamination  from  the  river-water  when  the  basins  are  built 
100  to  200  feet  from  the  river.  The  basin  is  constructed  next  di 
stream,  as  there  is  apt  to  be  a greater  flow  of  ground-water  there; 
besides  the  water  in  the  stream  can  make  up  any  deficiency  by 
use  of  proper  constructions. 

Filtration. — This  natural  filtration  of  water  through  the 
soil,  when  the  latter  is  good,  is  more  efficient  than  any  system  of 
ARTIFICIAL  FILTRATION,  which,  when  practiced  on  a large  scale, 
generally  consists  in  passing  water  through  layers  of  sand  and 
gravel  about  six  feet  deep.  The  finest  sand  is  put  at  the  top, 
the  upper  portion  of  which  catches  most  of  the  suspended  mat- 


WATER  SUPPLY. 


35 


ters,  and  by  the  oxygen  condensed  in  its  pores,  frees  the  water 
of  a small  portion  of  its  organic  matter. 

As  the  sand  becomes  clogged,  it  is  scraped  off  at  top  and  fresh 
sand  added. 

It  is  well  not  to  cause  the  water  to  flow  through  the  filter  at  a 
rate  greater  than  fifty  gallons  per  square  foot  of  surface  per  day. 
The  water  is  usually  several  feet  deep  on  the  filter-bed.  The 
beds  are  scraped  about  a dozen  times  a year,  oftener  in  summer 
than  in  winter. 

When  possible,  it  is  best  to  construct  settling-basins  where  the 
water  can  deposit  much  of  its  sediment  before  passing  on  to  the 
filter-beds. 

In  some  rivers,  the  particles  of  clay  in  suspension  are  so  fine 
as  to  readily  pass  through  sand  and  even  filter-paper.  In  such 
cases,  charcoal  pounded  fine  is  the  only  resource.  The  action  of 
a sand-filter  is  twofold,  mechanical  and  chemical: 

1st.  Mechanical,  in  that  suspended  matters  too  large  to  pass 
through  the  pores  of  the  filter  are  caught,  as  in  a net;  likewise 
much  sediment  that  would  otherwise  pass  through  sticks  to  the 
grains  of  sand,  due  to  the  property  of  adhesion. 

2d.  Chemical,  for  although  sand-filters  have  practically  no 
action  on  dissolved  mineral  matter,  yet  an  appreciable  quantity 
of  organic  matter  in  solution,  particularly  certain  kinds,  are 
removed  by  filtration  through  them. 

An  experiment  that  any  one  can  perform  will  illustrate  this: 
Add  a few  drops  of  sulphate  of  indigo  solution  to  some  clear 
water;  the  w|Lter  assumes  an  intense  blue  color,  which  color  it 
retains  on  filtering  through  an  ordinary  filtering-paper.  But  if 
we  strew  over  the  filter-paper  some  powdered  charcoal  (animal 
charcoal  is  best)  the  water  comes  through  perfectly  colorless.  If 
we  use  earth  in  place  of  the  charcoal,  the  water  that  passes 
through  it  is  slightly  colored,  thus  showing  that  earth  is  not,  so 
powerful  an  agent  as  charcoal.  Now,  evidently,  here  the  earth 
or  the  charcoal  have  exercised  a difierent  influence  from  the  filter- 
paper  alone.  The  filter-paper  will  catch  suspended  matter. 
Thus  muddy  water  passed  through  it  may  become  clear,  but  it 


36 


SANITARY  ENGINEERING. 


does  not  alter  chemically  the  substance  m solution.  We  have 
just  seen,  though,  that  earth  or  charcoal  does,  and  the  usual  hy- 
pothesis to  account  for  this  fact  is  that  ‘^porous  substances  con- 
dense gases — air,  oxygen,  etc.,  in  proportion  to  the  extent  of  their 
interior  surface/^  and  this  oxygen  actually  destroys  by  slow  com- 
bustion the  substance  in  question.  The  enormous  amount  of  sur- 
face to  volume  of  porous  charcoal  or  piles  of  earth  permits  the 
condensation  of  a large  amount  of  gas  which  stands  ready  to  attack 
any  chemical  body  that  can  be  decomposed  or  altered  by  it. 

Of  course  this  chemical  action  must  diminish  the  more  the 
longer  the  filter  is  in  action,  as  the  oxygen  is  not  so  readily  re- 
placed when  the  filter  is  covered  with  water.  If  water  is  really 
^polluted  by  sewage  matters,  it  has  been  shown  that  it  may  be 
improved  materially  but  not  perfectly  f)urified  by  filtration.  It 
is,  therefore,  pertinent  to  ask,  what  amount  and  kinds  of  organic 
matter  found  in  water  render  it. unfit  for  drinking? 

Evidently,  we  must  consider  the  two  questions  together.  Or- 
ganic matter,  per  se,  cannot  always  be  deleterious,  otherwise  soup 
would  have  to  be  ranked  as  poison.  It  is  stated  that  the  waters 
of  the  Dismal  Swamp,  saturated  with  organic  matter,  is  actually 
preferred  by  sea-going  vessels  to  purer  waters.  Chemistry  is 
perfectly  able  to  determine  the  mineral  salts  dissolved  in  water, 
and  medicine  can  pronounce  upon  the  amounts  that  may  be  taken 
into  the  system  without  injury.  Chemistry  can  likewise  deter- 
mine the  amounts  and  kinds  of  organic  matter  in  any  water,  and 
if  the  source  is  known  to  be  bad,  or  the  organic  matter  (espe- 
cially the  albuminoids)  in  excess  over  good  potable  waters  in  the 
vicinity,  the  chemist  is  able  to  form  an  intelligent  opinion,  at 
least  as  to  the  ‘^possible  amount  of  germ’^  or  disease-producing 
power  of  the  water. 

London  drinks  Thames  water  princij)ally,  though  above  the 
point  where  the  supply  is  abstracted  the  river  is  contaminated 
by  the  excrements  of  more  than  200,000  human  beings.’’ 

Those  who  favor  this  water,  claim  that  a polluted  river  puri- 
fies itself  in  its  ownward  flow,  the  noxious  matter  being  oxidized 
as  it  is  tossed  to  and  fro  by  the  current  and  thus  rendered  innoc- 


WATER  SUPPLY. 


37 


nous,  besides  being  more  and  more  diluted.  Again,  fish  eat 
fresh  fecal  matter,  and  vegetation  can  abstract  large  quantities  of 
it.  Still,  it  is  doubtful  if  this  natural  process  is  continued  long 
enough  to  thoroughly  destroy  the  hurtful  part  of  the  sewage. 

Now  can  this  Thames  water  be  regarded  as  a fit  source  for 
water  supply,  having  once  been  contaminated  to  a certain  extent? 

The  noxious  part  of  sewage  is  that  which  is  held  in  mechani- 
cal suspension,  and  these  globules  are  beyond  the  reach  of  the 
chemist,  and,  to  a great  extent,  of  the  raicroscopist.  There  are 
only  two  processes  by  which  it  can  be  etfectually  removed  ; the 
one  is  boiling  for  a long  time,  and  the  other  is  by  distillation, 
both  impracticable  on  a large  scale.^’  ^^No  process  of  filtration 
that  has  yet  been  devised  will  remove  choleraic  dejections  from 
water.^’  (Humberts  Water  Supply,  p.  19). 

The  organic  matter  is  not  then  considered  as  fatal  in  itself, 
but  as  dangerous,  when  of  certain  kinds,  as  atfording  a refuge 
and  breeding  ground  for  the  poison  germs  that  attend  an  epi- 
demic. A person  may  drink  even  diluted  sewage  with  but 
slight  inconvenience  until  this  germ  is  once  planted  in  it,  when 
at  once  his  beverage  changes  to  a rank  poison. 

Whether  we  accept  the  germ  theory  or  not,  it  is  admitted  that 
drinking  foul  water  and  breathing  impure  air  debilitate  the  sys- 
tem, and  thus  render  it  less  able  to  withstand  epidemics.  Let 
us  then  follow  the  natural  instincts  and  avoid  polluted  air  and 
water,  especially  as  North  Carolina  can  afford  the  pure  articles 
in  such  abundance. 

Lead  Poisoning. — There  is  one  source  of  poisoning  that  may 
be  considered  by  itself — lead  'poisoning^  due  to  the  use  of  lead 
cisterns  and  lead  pipes. 

Soft  waters  that  contain  oxygen  oxidize  the  lead  and  then  dis- 
solve the  lead  oxide  formed.  Hard  waters  containing  free  car- 
bonic acid,  form,  on  the  contrary,  carbonate  of  lead,  which  is 
only  soluble  to  the  extent  of  one  part  in  seven  thousand,  unless 
there  is  much  free  carbonic  acid  present,  darkens  softening 
process  lessens  the  action  of  water  on  lead.  Peaty  matters  form 
a sort  of  protecting  coating  on  the  lead  pipe  that  is  very  effica- 


38 


SANITARY  ENGINEERING. 


cious  in  preventing  further  action  on  the  lead.  One-tenth  of  a 
grain  of  lead  per  gallon  of  water  may  produce  lead  poisoning  in 
time. 

The  presence  of  lead  in  water  is  easily  detected  by  passing  a 
current  of  sulphurated  hydrogen  through  a deep  column  of  the 
acidified  water.  If  the  liquid  becomes  tinged  of  a brown  color, 
it  is  due  to  the  formation  of  lead  sulphide.  What  is  the  remedy 
if  the  water  is  found  to  act  continuously  on  the  lead?  Simply 
abolish  the  lead  cisterns  for  slate,  or  stoneware,  or  galvanized 
iron  cisterns,  and  replace  the  lead  pipes  by  wrought-iron  pipes 
with  screw  joints.  The  tin-lined  lead  pipe  has  not  proved  satis- 
factory ; a small  flaw  exposes  the  lead,  a galvanic  action  between 
the  two  metals  is  commenced,  and  the  water  is  speedily  poisoned. 

It  is  of  the  greatest  importance  to  observe  that  no  cistern  or 
water-pipes  should  be  placed  where  sewer  gases  may  pass  either 
through  or  over  them,  in  contact  with  the  water,  since  water  is 
very  absorbent  of  such  gases. 

Cistern  Water. — Where  rain-water  is  used  as  the  source 
of  supply,  it  is  collected  from  the  house  roofs  and  stored  in  cis- 
terns of  wood  or  brick  in  cement.  The  cistern,  if  of  wood, 
should  have  a circular  form  ; if  of  brick,  any  convenient  form 
can  be  used,  provided  the  earth  is  well  rammed  behind  the  walls, 
to  enable  the  latter  to  withstand  the  outward  pressure  of  the 
water.  The  cistern  should  be  covered  and  ventilated. 

The  rain-water  as  it  descends  brings  down  many  impurities 
from  the  atmosphere,  such  as  soot,  acid  fumes,  oil,  etc.,  particu- 
larly in  the  manufacturing  centres;  besides  if  organic  impurities 
in  the  shape  of  dust,  such  as  horse  manure,  etc.,  cover  the  roof, 
the  water  is  further  contaminated  before  it  reaches  the  cistern. 
The  character  of  the  roof  likewise,  whether  lead-painted,  formed 
of  new  shingles  or  decayed  ones,  etc.,  must  be  considered.  We 
thus  see  that  cistern  water  is  not  necessarily  perfect,  though  it  is 
probably  better  than  well  waters,  for  while  it  has  not  had  the 
benefit  of  the  natural  filtration  of  the  latter,  still  it  has  taken  up 
no  new  salts  from  the  ground,  and  has  certainly  escaped  sewage 
contamination. 


WATER  SUPPLY. 


39 


Nevertheless,  it  should  be  filtered  before  being  used.  This  is 
effected  in  various  ways.  One  plan,  when  the  brick  cistern  is 
used,  is  to  divide  the  cistern  by  a porous  wall  into  two  unequal 
parts.  The  foul  water,  let  into  the  larger  divisions,  filters 
through  the  porous  wall  into  the  smaller  division,  from  whence 
it  is  pumped  over  the  house.  The  porous  wall  may  be  made  of 
soft  bricks,  or  of  some  filtering  material,  as  porous  tiles  or  blocks 
of  animal  (bone)  charcoal,  that  may  be  placed  in  a frame  which 
can  slide  in  groves  and  be  readily  replaced  when  the  filter  has 
become  clogged  up. 

The  brick  wall,  although  very  efficient  at  first,  becomes  clog- 
ged up  in  a few  mouths  by  solid  matter,  consisting,  amongst 
other  things,  of  insects,  worms,  etc.;  so  that  the  filtration  then  is 
rather  an  injury  than  a benefit,  as  chemical  analysis  has  demon- 
strated. The  solid  matters  that  settle  at  the  bottom  of  cisterns 
should,  of  course,  be  removed  whenever  practicable. 

Domestic  Filters. — With  regard  to  domestic  filters  of  any 
kind  whatsoever,  it  may  be  observed  that  the  filtering  material 
requires  renewal  every  few  months. 

The  following  is  an  extract  from  the  “Sixth  Report  of  the 
River  Pollution  Commissioners  of  England 

“ It  cannot  be  too  widely  known  that,  as  a rule,  domestic  filters 
constructed  with  sand,  or  sand  and  wood  charcoal,  are  nearly 
useless  after  the  lapse  of  four  months,  and  positively  deleterious 
after  the  lapse  of  a year.’’ 

“Of  all  material  for  domestic  filtration,  with  which  we  have 
experimented,  we  find  animal  (bone)  charcoal  and  spongy  iron 
to  be  the  most  effective  in  the  removal  of  organic  matter  from 
water.” 

“The  removal  of  mineral  constituents,  and  the  consequent 
softening  of  the  water,  ceases  in  about  a fortnight,  but  the  with- 
drawal of  organic  matter  still  continues,  though,  to  a greatly 
diminished  extent,  when  the  filter  is  much  used,  even  after  the 
lapse  of  six  mouths.” 

“ We  found  that  myriads  of  minute  worms  were  developed  in 
the  animal  charcoal,  and  passed  out  with  the  water  when  the  fil- 


40 


SANITARY  ENGINEERING. 


ters  were  used  for  Thames  water,  and  when  the  charcoal  was  not 
renewed  at  sufficiently  short  intervals,  a serious  drawback  to  its 
use.’^ 

The  spongy  iron  is  free  from  this  trouble,  but  the  filtered 
water,  especially  the  first  portions  filtered,  contain  iron;  and  the 
softer  the  water  the  more  iron  dissolved. 

On  the  whole,  it  would  seem  that  for  hard  waters  ‘^Bischop’s 
Spongy  Iron  Filter is  best,  though  the  animal  charcoal  is  an 
admirable  material,  when  renewed  every  few  months.  Chemical 
analysis  can  alone  tell  when  the  filter  has  ceased  action. 

Both  materials  (spongy  iron  and  animal  charcoal)  remove 
about  the  same  quantity  of  ‘‘albuminoid  ammonia,^’  say  one- 
fourth,  as  a means  of  some  very  careful  experiments  (Nichols  on 
Filtration  of  Potable  Water),  this  substance  being  taken  as  the 
measure  of  the  suspicious  organic  matter  in  solution, 

From  an  analysis  by  Bischof  (Humber’s  Water  Supply)  it 
would  seem  that  the  spongy  iron  (a  metallic  iron  reduced  from 
an  oxide  without  fusion,  and  hence  in  a loose  spongy  state)  was 
a more  efficient  agent  than  “magnetic  carbide”  and  “silicated 
carbon,”  two  other  materials  that  have  been  used  with  success. 

If  animal  charcoal  is  used,  it  should  be  in  lumps  in  preference 
to  blocks,  though  the  latter  gives  good  results.  An  admirable 
filter,  that  may  be  used  in  any  cistern,  consists  of  a metallic  ves- 
sel with  a perforated  bottom,  filled  with  animal  charcoal  and 
having  a pipe  leading  from  the  to[),  wliich  must  be  below  the 
level  of  the  water  in  the  cistern.  The  water  of  the  cistern  passes 
up  through  the  perforated  bottom,  then  filters  through  the  char- 
coal and  is  drawn  off  by  the  pipe  when  it  is  needed.  The  advan- 
tage of  this  arrangement  is  this:  the  suspended  articles  are  caught 
mostly  at  the  bottom  of  the  filter  and  may  become  detached  from 
the  filter,  especially  if  water  is  forced  through  it  from  the  top  in 
a downward  direction,  at  intervals.  The  filter  can  of  course  be 
taken  out  at  any  time  and  the  material  aerated  or  renewed.  Many 
other  materials  have  been  used  for  filters  of  small  size — sponge, 
sand,  cotton,  flannel,  earthenware,  common  charcoal,  etc.  The 
small  size  filter  acts  simply  as  a strainer  in  a short  time,  and  re- 


AVATER  SUPri.Y. 


41 


quires  frequent  renevvinp^,  otherwise  it  is  worse  than  useless. 
Makers  of  all  kinds  of  filters,  however,  do  not  hesitate  to  aver 
that  they  are  self-cleansing,  perfect,  etc.,  etc.,  which,  we  have 
seen,  is  opposed  to  the  best  and  latest  scientific  research  on  the 
subject.  Let  the  householder  be  guided  by  the  facts. 

Where  nothing  better  is  at  hand,  water  may  be  filtered  through 
a box,  perforated  at  the  bottom,  containing  clean  quartz  sand, 
resting  on  a plate  of  })orous  earthenware  or  on  bricks  placed  on 
top  of  the  charcoal.  Expose  the  filter  to  the  air  from  time  to 
time. 

Public  Systems  of  Water  Supply. — It  will  probably  not 
be  long  before  our  cities  will  demand  })urer  water  than  can  be 
supplied  by  the  wells  and  springs  now  used;  many  of  them  be- 
ing, without  doubt,  polluted  by  the  many  impurities  thrown  on 
the  surface.  This  involves  a public  system  of  Avater  supply,  with 
its  attendant  system  of  reservoirs,  filter-beds,  pipes,  hydrants,  etc. 
In  view  of  such  contingency,  it  may  not  be  out  of  place  to  men- 
tion some  of  the  requirements  that  such  a system  should  fulfill. 
. The  water  may  be  obtained  from  lakes,  rivers  and  streams, 
springs  and  wells,  impounding  reservoirs  often  being  used  to 
collect  that  which  falls  on  the  hill-sides  into  one  place. 

This  water  may  be  conveyed  for  distribution  (Rawlinson’s 
Suggestions  to  Local  Sanitary  Boards,  England,  p.  20), — 

^^By  means  of  open  conduits  (before  filtration); 

covered*  (always  after  filtration); 
cast-iron  pipes  under  pressure.^’ 

A water  supply  may  be  gravitating,  or  the  water  may  be 
pumped  by  steam  power.  The  relative  economy  of  one  or  the 
other  form  of  works  will  depend  on  details  of  cost  and  quality 
of  water;  as  a rule,  gravitating  works  require  the  largest  capi- 
tal. The  annual  working  expenses  of  a pumping  scheme  may, 
however,  be  greatest.  Reservoirs  for  service  distribution  should 
be  covered. 

If  filters  are  used,  the  water  should  not  be  exposed  in  open 
reservoirs  and  tanks  after  filtration. 


^Covered,  to  prevent  the  growth  of  vegetable  organisms. 


42 


SANITARY  ENGINEERING. 


Cast-iron  pipes,  properly  varnished,  should  be  used  for  street 
mains.  Lead  should  not  be  used  with  soft  water,  either  in  ser- 
vice pipes  or  in  cisterns.  Wrought-iron  tubes  with  screw  joints 
may  be  used  for  home  service. 

Water  at  and  below  six  degrees  of  hardness  is  considered  soft 
water;  above  this  range,  water  is  termed  “hard.^’  ' 

These  suggestions^^  of  Mr.  Rawlinson,  (Chief  Engineering 
Inspector  to  the  local  government  board,  London),  are  valuable,.. 
especially  as  they  represent  the  best  modern  thought  on  this  sub- 
ject, and  may  tend  to  prevent  fatal  mistakes  in  designing  water- 
supply  systems. 

As  he  says,  ^^The  great  modern  improvement  in  water  supply 
is  the  delivery  by  constant  service,  and  at  high  pressure,  over  the 
entire  area  of  a town,  and  into  every  house,  cottage  and  tenement,, 
and  should  be  secured  where  practicable.’^ 

The  ‘^constant  supply  at  high  pressure”  permits  consumers  to 
draw  water  from  the  pipes  at  any  time,  and  can  be  made  so  effi- 
cacious in  the  extinction  of  fires  as  to  diminish  their  destructive 
effects  most  materially.  Fire-engines  are  not  needed  with  such 
a system.  It  is  said  that  in  Paris,  owing  to  the  excellent  organ- 
ization of  the  fire  department,  that  a destructive  fire  is  almost 
unknown.  The  intermittent  supply  does  not  offer  these  advan- 
tages. House  cisterns  are  required  to  stow  the  daily  allowance 
of  water,  which  is  only  supplied  at  certain  hours.  The  cisterns, 
if  neglected,  may  not  be  supplied  with  water,  or  they  may  leak, 
or  absorb  foul  gases,  and  finally  suffer  from  want  of  cleanliness. 

There  is,  besides  the  high  pressure  due  to  a sufficient  elevation 
of  the  reservoir  above  the  town,  the  Holly  System^^  of  main- 
taining this  high  pressure  in  the  pipes  by  steam  power.  The 
pumping  machinery  is  placed  near  the  water,  which  is  pumped 
directly  into  the  mains,  the  pressure  being  kept  constant,  or 
.increased  or  diminished  at  will. 

This  system  is  highly  spoken  of  wherever  it  has  been  tried. 

Source  op  Supply.  Available  Rain-fall. — In  any  one 
of  these  systems,  it  is  a first  requisite  that  the  source  of  supply 
shall  be  constant  and  unfailing.  Where  a large  stream  is  used 


WATER  SUPPLY. 


43 


as  the  source,  the  amount  that  can  be  depended  on  in  the  dryest 
seasons  may  be  estimated  with  some  degree  of  certainty.  Where 
small  lakes,  springs,  wells  and  small  streams  are  used  as  the 
source,  we  have  to  depend,  more  or  less,  on  the  observed  rain-falls 
for  the  different  seasons,  in  conjunction  with  the  measured  flow 
of  the  streams,  if  any  to  form,  at  best,  only  an  approximate  esti- 
mate of  the  yield. 

Such  observations  should  be  conducted  over  a period  of  twenty 
years  if  possible,  to  include  all  fluctuations;  but  as  a rule,  in  this 
State,  we  have  only  a few  years  observations  of  rain- fall,  and 
only  one  or  two  of  the  flow  of  streams  to  found  an  estimate  upon 
of  the  probable  yield  of  water  over  a given  drainage  area. 

Let  us  suppose  that  an  embankment  is  thrown  across  a valley, 
to  form  a reservoir,  into  which  shall  be  stored  all  the  water  that 
drains  into  the  valley  from  its  catchment  grounds,^’  whose  area 
can  be  readily  computed,  as  it  is  bounded  generally  by  well  defined 
ridge  lines  and  the  embankment  in  question.  Now  the  yearly  rain- 
fall in  different  portions  of  the  State  varies  from  20  to  60  odd 
inches,  the  average  being  high,  over  45  inches  certainly.  If  all  of 
this  could  be  collected  into  reservoirs,  the  amount  would  be  given 
by  simply  multiplying  the  catchment  area  by  the  depth  of  the  rain- 
fall; thus,  if  the  catchment  area  was  one  square  mile,  27,878,- 
400  square  feet,  and  the  depth  of  rain-fall  one  foot,  we  should 
have  27,878,400  cubic  feet  in  a year  or  76,379  cubic  feet  in  one 
day  for  the  supply.  But  in  practice  we  are  very  far  from  secur- 
ing the  whole  rain-fall,  the  reason  for  which  can  be  made  plain 
by  the  following  considerations: 

Let  us  first  suppose  the  catchment  ground  to  be  impermeable 
and  free  from  vegetation;  then  any  rain  that  falls  all  flows  into 
the  reservoir,  except  that  lost  by  evaporation;  the  latter  being 
less  as  the  surface  is  steeper,  the  temperature  lower  and  the  drain- 
age area  smaller. 

If,  however,  the  surface  of  the  ground  is  pervious^  as  is  usual, 
then  a portion  of  the  rain-fall  sinks  into  the  ground,  to  appear 
again  as  springs,  and  thus  drain  ultimately  into  the  reservoir,  or 
else  to  pass  off  by  some  subterranean  stratum  to  other  outlets. 


44 


SANITARY  ENGINEERING. 


Id  this  case  the  amount  lost  by  evaporation  is  less  as  the  ground 
is  more  absorbent  and  better  drained,  the  slopes  steeper,  and  the 
temperature  and  area  smaller.  If  now  we  suppose  the  earth 
more  or  less  clothed  with  vegetation,  the  latter  absorbs  and  partly 
evaporates  still  more  water.  The  conditions  of  the  problems  are 
thus  seen  to  vary  greatly  for  different  localities,  with  the  season 
of  the  year,  and  it  may  be  added,  also  with  the  winds  and  rela- 
tive humidity  of  the  atmosphere. 

In  England,  where  observations  have  been  conducted  for  years 
over  many  distinct  catchment  basins,  the  loss  due  to  evaporation 
and  absorption  has  been  found  to  range  from  nine  to  nineteen 
inches  per  annum,  and  it  is  the  practice  to  consider  as  available 
no  more  than  the  mean  fall  for  three  consecutive  dry  years  (which 
is  found  to  be,  as  a rule,  I less  than  the  average  rain-fall),  after 
subtracting  the  loss  by  evaporation.  Thus,  if  the  mean  fall  for 
three  consecutive  dry  years  is  about  forty  inches,  and  if  the  loss 
by  evaporation  and  absorption  is  put  at  20  inches,  this  would 
leave  20  inches  of  rain-fall  that  could  be  utilized  if  it  was  all 
stored. 

Observations  on  Lake  Cochituate,  Mass.,  water-shed  of  12,077 
acres,  from  1852  to  1875,  gave  a yearly  rain-fall  varying  from 
35  to  69  inches — average  50,  and  the  percentage  of  this  received 
into  the  lake  25  to  74 — average  about  45.  It  is  nevertheless 
recommended  by  some  good  engineers  that  not  over  12  to  15 
inches  of  rain-fall  be  counted  on  as  available  in  the  United  States, 
which  is  less  than  Humber  allows. 

The  evaporation  from  the  surface  of  the  water  in  the  reservoir, 
in  dry  seasons,  averages  about  inch  daily  in  England,  whilst 
it  is  as  much  as  J inch  in  some  localities  in  India.  The  annual 
loss  in  England  is  put  at  20  to  25  inches.  It  is,  of  course,  much 
more  in  small  and  shallow  ponds,  which  can  be  more  readily 
heated,  than  in  extensive  reservoirs  or  lakes.  Trautwine  says 
that  the  daily  loss  from  evaporation  in  the  three  warmest  months 
of  the  year  will  rarely  exceed  A inch  in  any  part  of  the  United 
States.  This  is  probably  too  high,  for  the  same  authority  found 
in  the  tropics  over  a pond  8 feet  deep,  a loss  of  only  2 inches  in 


WATER  SUPPLY. 


45 


16  days,  or  ^ inch  per  day.  The  thermometer  reached  115°  to 
125°  in  the  sun  every  day.  It  is  evident  from  the  foregoing  the 
importance  of  early  making  observations  in  each  locality  for  as 
long  a period  as  possible,  in  order  to  ascertain  the  ratio  of  the 
‘^available’’  to  the  “totaP^  rain-fall.  Rankine  says  that  this 
ratio  is  about  1 for  hard  rocks,  roof  surfaces,  paved  streets,  &c., 

to  for  pastures,  to  ^ for  flat  cultivated  country,  and  0 
for  chalk.  It  follows  that  a catchment  basin  is  best  located  in 
the  older  formations,  consisting  of  hard  rocks,  whilst  wells  suit 
best  the  more  previous  and  recent  deposits.  London  is  even  now 
preparing  to  give  up  the  Thames  water  altogether  and  draw  her 
supply  from  her  underlying  chalk  beds. 

It  is  important  to  note  that  the  most  reliable  method  of  ascer- 
taining the  available  rain -fall  is  to  measure  the  actual  discharge 
of  streams  that  drain  a given  water-shed.  Then,  by  comparison 
with  the  total  rain-fall  on  the  water-shed,  we  find  the  actual 
amount  lost  by  evaporation  and  absorption  of  the  ground. 

No  town  which  contemplates  a public  water  supply  should 
neglect  to  have  such  observations  made,  covering  a period  as  long 
as  possible,  to  take  proper  account  of  droughts,  &c. 

Consumption  per  Head. — Statistics  show  that  in  England 
the  daily  amount  of  water  used  in  the  towns  and  cities  varies  from 
15  ^0  50  gallons  per  head — 30  being  regarded  as  a full  allowance. 
In  the  United  States  the  daily  consumption  per  head  varies  from 
25  to  120  U.  S.  liquid  gallons  of  231  cubic  inches  (1  cubic  foot 
— 7.48052  gallons);  and  it  is  recommended  by  some  to  allow  40 
to  50  gallons  per  head  for  smaller  cities,  and  an  increasing  amount 
as  the  population  increases. 

It  is  very  plain,  from  the  records,  that  an  enormous  waste 
occurs  in  our  cities,  and  special  attention  is  now  being  directed 
to  it.  Where  inspections,  or  water  meters  have  been  tried,  the 
amount  consumed  has  often  been  reduced  to  half  and  even  one- 
third  the  original  amount.  Humber  estimates  that  20  to  25  gal- 
lons is  a liberal  allowance.  Even  if  we  assume  double  this,  it 
still  behooves  us  to  take  every  precaution  to  avoid  waste  by  the 
use  of  meters  or  otherwise;  else  the  large  yearly  cost  of  the  water 
supply  may  be  needlessly  doubled  or  trebled. 


46 


SANITARY  ENGINEERING. 


Reservoir  Capacity. — Well,  assuming,  say  45  gallons,  the 
daily  demand  on  a reservoir  is  made  up  of  the  45  gallons  X 
number  of  population,  plus  the  daily  evaporation  from  the  sur- 
face of  the  water,  plus  any  compensation  water  to  mill-owners 
or  others.  Subtracting  from  this  the  dry  weather  flow  of  the 
streams  discharging  into  the  reservoir,  we  get  ^^the  excess  of  the 
demand  over  the  supply  in  dry  months;  and  this  multiplied  by 
the  number  of  days  storage  of  the  reservoir,  gives  its  available 
capacity,  or  the  volume  it  must  contain  between  its  highest  and 
lowest  working  levels.  Some  advise  that  every  storage  reservoir 
should,  if  possible,  contain  six  months  of  the  excess  of  the  daily 
demand  above  the  daily  supply  for  the  dryest  consecutive  six 
months.  Some  English  engineers  formulate  the  following  rule, 
as  the  result  of  considerable  experience:  ^‘The  number  of  days 
storage  of  reservoir^’  equals  the  number  1,000  divided  by  the 
square  root  of  the  rain-fall  in  inches  for  three  consecutiv’^e  dry 
years.  Thus,  if  this  rain-fall  is  36  inches,  the  reservoir  should 
contain  l,000-f-6=166.7  days  storage;  that  is,  166.7  times  the 
excess  of  the  demand  over  the  dry  weather  su[)ply. 

The  following  table  (see  ^^Engineering  News,’’  August  23, 
1879)  will  show  the  great  disparity  between  the  least  and  great- 
est flow  of  streams: 

/ 


Name  of  River. 

Drainage  Area 
in 

FLOW  IN  CUB.  FT.  PER  SQ.  MILE. 

Square  miles. 

Greatest  Flow. 

Least  Flow. 

Connecticut, 

10,234 

20.27 

0.51 

Merrimack, 

4,136 

23.40 

0.53 

Schuylkill, 

Tyne,  England, 

1,800 

1,100 

80.23 

0.21 

Passaic, 

981 

20.33 

0.23 

Croton, 

339 

74.87 

0.15 

Concord,  

352 

12.64 

0.17 

Hackensack, 

Sudbury, 

84 

76 

41.60 

0.33 

0.05 

Croton,  W.  Branch,. 

20 

54.43 

0.02 

These  flgures  show  that  on  large  drainage  areas  the  propor- 
tional flow  is  less  in  freshets  and  greater  in  dry  seasons  than  on 
small  areas.” 


WATER  SUPPLY. 


47 


The  ^Meast  flow”  given  above  is  probably  the  least  flow  on 
any  day  of  the  dry  season.  If,  however,  our  reservoir  is  to  con- 
tain, say  6 months^  supply,  then  we  desire  to  know  the  least  aver- 
age flow  for  any  six  months  during  20  or  more  years.  Suppose 
this  to  be  0.2  cubic  feet  per  second  per  square  mile  of  drainage 
area,  or  17,280  cubic  feet  per  day  per  square  mile. 

Suppose  a population  of  10,000  consuming  daily  6 cubic  feet 
(45  gallons,  say)  per  head,  or  60,000  cubic  feet  in  all;  and  that 
the  loss  by  evaporation  from  the  reservoir  of  10  acres  say,  is  J 
inch  daily,  or  about  5,000  cubic  feet.  The  total  daily  demand 
is  thus  65,000  cubic  feet,  which  is  about  48,000  cubic  feet  in 
excess  of  the  supply  from  the  stream ; so  that  if  the.  reservoir  is 
to  contain  6 months=180  days  of  this  excess,  its  available 
capacity  must  be  48,000X180=8,640,000  cubic  feet,  or  an  aver- 
age available  depth  over  the  10  acres  of  20  feet. 

It  is  evident  that  if  the  daily  demand,  as  above,  is  65,000 
cubic  feet,  the  yearly  demand  thus  being  23,725,000  cubic  feet, 
that  but  little  over  10  inches  of  rain-fall  over  the  1 square  mile 
of  drainage  area  has  been  secured,  since  10  inches  on  a square 
mile  gives  only  23,232,000  cubic,  feet.  This  is  certainly  within 
reasonable  bounds. 

No  allowance  is  made  above  for  compensation  to  mill-owners. 

Of  course,  by  building  the  reservoir  of  sufficient  capacity  the 
whole  of  the  rain-fall,  minus  the  loss  by  absorption,  evaporation 
and  leakage,  can  be  utilized ; but  it  has  not  been  found  desirable 
to  build  such  huge  reservoirs  in  actual  practice,  so  that  much  of 
the  rain-fall  is  purposely  allowed  to  run  off. 

Sources  of  Water  Supply  m N.  C. — Maintei^ance  of 
Purity. — This  State  is  abundantly  supplied  with  unfailing 
sources  of  water  supply  in  her  many  rivers  nnd  lakes,  not  to 
speak  of  the  underground  water,  which  hitherto  has  been  the 
only  source  used  in  the  supply  of  her  largest  towns.  What  a 
contrast  do  the  rivers  and  streams  of  England — many  of  them 
fouled  to  inky  blackness  by  the  refuse  of  thousands  of  manufac- 
tories— present  to  our  own  waters,  teeming  with  fish  and  drink- 
able almost  everywhere.  It  is  to  be  hoped  that  the  enacting  of 


48 


SANITAEY  ENGINEERING. 


wise  laws  will  maintain  their  purity,  by  forbidding  any  injurious 
waste  or  crude  sewage  from  entering  them.  If  this  system  is 
inaugurated  from  the  beginning,  much  trouble  may  be  avoided. 
England  now  is  making  a brave  effort  to  regain  the  pristine 
purity  of  her  streams;  let  us  be  careful  not  to  lose  this  thing  of 
beauty  in  our  own  waters. 

The  foregoing  notes  are  very  brief,  but  they  may  contain  some 
useful  hints  to  our  larger  towns  and  cities,  who  will,  sooner  or 
later,  abolish  the  polluted  well  and  adopt  a public  system  of 
water  supply. 


CHAPTER  IV. 

SEWERAGE  SYSTEMS. 

WATER  SEWERAGE. 

Then  will  likely  follow  the  complex  system  of  water  sewerage, 
which  is  now  regarded  as  the  best  for  the  largest  cities;  though 
it  is  admitted  that  it  is  a delicate  machinery  and  requires  the 
greatest  care  in  its  manipulation. 

This  system  has  been  so  thoroughly  studied  that  a sufficient 
literature  exists  on  the  subject  to  answer  the  needs  of  practice ; 
so  that  it  is  needless  to  enter  into  any  very  technical  discussion 
of  it  here. 

Conditions  that  the  system  should  fulfill. — The  ob- 
ject to  be  accomplished  by  the  system  is  to  carry  all  offensive 
matters  underground,  and  as  rapidly  as  possible,  out  of  the  city, 
by  the  aid  of  the  water  used  in  the  houses  and  the  rain-water  that 
falls.  The  proper  carrying  out  of  a system  of  this  kind  requires 
the  aid  of  enlightened  sanitary  engineers  of  experience;  above 
all,  in  the  general  design.  Let  it  be  borne  in  mind  by  any  town 
contemplating  the  water  system,  that  an  error  in  design,  like  the 
bad  foundation  to  a structure,  is  often  very  difficult  to  remedy. 

Special  emphasis  is  laid  on  the  principle,  that  the  sewage 
should  be  carried  out  of  the  town  limits  quickly — say  in  24  hours, 


WATER  SEWERAGE. 


49 


or  less,  when  prncticable.  This  is  effected  l)y  a correct  adjust- 
ment of  the  size  and  shape  of  the  sewer  to  its  fall,  having  assumed 
* the  total  amount  of  sewage  that  is  to  be  provided  for  daily.  The 
question  is  one  of  hydraulics,  and  may  be  solved  by  the  use  of 
well  kpown  formulae  for  the  flow  of  water  in  channels. 

Example. — As  an  illustration,  take  the  following,  from 
“Rawlinsoifls  Suggestions’^:  ^‘The  sewage  of  a town  or  village 
will  consist  of  waste-water  and  excreta  from  the  houses,  and  the 
volume,  in  round  figures,  may  range  from  100  to  250  gallons 
per  day  from  each  house.  This  volume  will  probably  flow  off 
in  about  eight  hours,  so  that  the  sewers  must  provide  for  not  less 
than  three  times  this  volume,  if  even  every  drop  of  roof  and 
surface-water  can  be  excluded.  It  is  more  usual  to  assume  that 
one-half  the  daily  quantity  is  discharged  in  from  6 to  8 hours.  ^ 
As  this  cannot  in  all  cases  be  accomplished,  the  sewers  should 
provide  for  not  less  than  1,000  gallons  from  each  house;  or  for 
a town  of  1,000  houses  (5,500  population)  have  a delivering 
capacity  of  about  1,000,000  gallons  (daily).  An  outlet  sewer  of 
2 feet  diameter,  laid  with  a fall  of  5 feet  per  mile,  will  deliver 
upwards  of  2,000,000  gallons,  flowing  a little  more  than  half 
full.  Lesser  diameters  will  answer  where  there  are  greater  falls.” 

A 2-feet  sewer  thus  provides  for  doubling  the  population  in  a 
few  years. 

Now  100  to  250  gallons  per  day,  from  each  house,  containing 

persons,  corresponds  to  from  18.2  to  45.5  gallons  per  day  for 
each  person,  wdiich  figures  represent  about  the  extremes  in  Eng- 
lish practice;  30  gallons  being  the  usual  allowance,  excluding 
rain-water. 

In  the  case  above,  the  velocity  of  the  sewage  of  11,000  per- 
sons is  about  2 feet  per  second,  which  is  the  minimum  velocity 
in  order  that  so  small  a sewer  may  be  self -cleansing. 

As  the  velocity  is  less  for  the  real  population  of  5,500,  espe- 
cially if  they  use  less  water  than  1,000,000  gallons,  the  inclina- 
tion of  the  sewer  should  be  increased  if  possible,  or  ‘^flushing” 
will  have  to  be  resorted  to,  or  the  sewer  must  be  made  smaller 
than  the  2-feet  diameter,  to  secure  the  proper  velocity  to  make 
4 


50 


SANITARY  ENGINEERING. 


the  sewer  self-cleansing,  and  to  prevent  the  formation  of  the 
poisonous  sewer  gases,  whicih  are  always  formed  when  the  pro- 
gress of  the  sewage  out  of  the  town  is  slow,  in  spite  of  all  the 
ventilation  schemes  that  may  be  tried. 

A circular  sewer,  one  foot  in  diameter,  running  half  full,  at 
an  inclination  of  1 to  600  will  discharge  46.3  cubic  feet  per 
minute,  at  a velocity  of  118  feet  per  minute,  equivalent  to  a dis- 
charge of  167,000  gallons  (in  round  numbers)  in  8 hours.  This 
is  slightly  over  the  discharge  of  5,500  persons,  allowing  30  gal- 
lons to  each  person,  so  that  this  one-foot  seWer  would  suffice  if 
rain-water  is  to  be  disregarded. 

Amount  of  rain-fall  to  pass  into  sewers. — Let  us 
next  ascertain  the  size  of  a sewer  on  the  supposition  that  the 
town  is  one  square  mile  in  area,  and  that  a rain-fall  of  one  inch 
in  24  hours  actually  drains  into  it.  The  rain-fall  is  '*2,323,200 
cubic  feet  in  24  hours;  or  at  the  rate  of  1,613  cubic  feet  in  one 
minute.  By  use  of  proper  formulae,  it  is  found  that  an  egg- 
shaped  sewer,  3J  by  5 feet,  ruFlning  full,  will  discharge  the  water 
at  a velocity  of  3f  feet  per  second,  the  inclination  being  taken, 
as  at  first,  at  only  5 feet  to  the  mile. 

We  can  now’ readily  see,  by  this  particular  example,  how  much 
the  size,  and  hence  the  cost,  of  sewers  is  increased  by  making 
provision  to  receive  the  rain-fall.  It  is,  of  course,  far  more 
expensive  to  provide  for  the  exceptionally  heavy  rain-falls  (as 
^‘6  inches  in  2 hours,’’  etc.)  which  sometimes  occur.  Sewerage 
systems  in  this  country  do  not  provide  for  such  exceptional  rain- 
falls. 

The  London  intercepting  sewers  were  constructed  to  carry  ^ 
inch  rain-fall  in  24  hours,  at  the  time  of  maximum  flow  of  sew- 
age, larger  amounts  being  provided  for  by  storm-water  overflows. 

It. is  found  that  different  soils,  or  surfaces,  have  not  the  same 
absorptive  power;  thus  in  London  the  sewers  in  some  sections 
deliver  one-half  the  rain-fall,  whilst  in  entirely  paved  streets, 
nearly  the  whole  of  the  water  is  drained  into  them. 

Latham  says  that  in  Croyden,  the  soil  being  porous,  gravel 
overlying  chalk,  ‘^the  amount  of  rain  contributed  by  a storm  of 


WATER  SEWERAGE. 


51 


.72  inch  in  12  hours,  did  not  yield  more  than  one-tenth  of  it  to 
the  sewers.’’  More  impervious  districts  required  the  full  allow- 
ance of  1 inch  in  24  hours,  together  with  the  sewage.  In  Dant- 
zic,  which  is  sandy  and  flat,  J inch  in  24  hours,  together  with  2 
cubic  feet  of  sewage  in  8 hours  was  assumed  as  the  basis  for 
computations. 

In  the  records  of  ‘^British  Rain-fall”  for  1880,  1881  and 
1882,  there  are  reported  fifty -seven  falls  at  a rate  of  over  1 inch 
per  hour,  forty-two  over  IJ  inch,  thirty  over  IJ  inch,  eighteen 
over  2 inches,  six  over  3 inches,  and  two  over  5 inches  per  hour. 
The  heaviest  fall  reported  was  at  the  rate  of  5.8  inches  per  hour, 
and  it  continued  for  30  minutes. 

Very  few  records  of  the  intensity  of  heavy  falls  have  been 
kept  in  this  country,  but  the  observations  taken  for  a number  of 
years  at  Brooklyn  and  Providence  do  not  indicate  such  heavy 
falls  as  are  recorded  above,  and  it  is  recommended  by  Julius  W. 
Adams,  C.  E.  (“  Sewers  and  Drains,”  p.  30),  to  provide  for  car- 
rying oflP  one  inch  of  rain  falling  in  an  hour,  for  greater  storms 
occur  at  such  long  intervals  that  the  damage  done  would  be  com- 
paratively insignificant;  further,  it  is  recommended,  for  large 
areas,  to  consider  only  one-half  of  this,  i.  e.,  J inch,  as  running 
off  through  the  main  sewers  in  one  hour,  which  is  equivalent  to  J 
cubic  foot  per  second  discharge  for  every  acre  very  nearly. 

None  of  the  very  few  observations  made  of  the  proportion  of 
the  rain-fall  reaching  the  outlet  of  the  sewers  in  a given  time 
indicate  as  much  as  one-half  the  actual  rain-fall,  and  generally 
it  is  very  much  less,  varying,  of  course,  with  the  character  and 
slope  of  the  surface  on  which  it  falls,-  as  well  as  on  the  fall  of 
the  branch  sewers,  the  evaporation  from  the  surface  and,  the  ab- 
sorption by  the  soil.  Of  course,  on  a very  limited  paved  area, 
the  whole  of  the  rain-fall  may  be  taken  as  flowing  through  the 
sewers  in  the  time  of  its  fall,  and  on  very  large  areas  much  less 
than  one-half  can  be  estimated  with  safety.  It  is  plain,  though, 
that  storm-overflows  must  be  provided  to  carry  off  any  excess  of 
an  exceptional  heavy  rain-fall  to  prevent  gorging  of  the  main 
sewers — in  fact,  branch  sewers  may  be  designed  to  carry  much 


52 


SANITARY  ENGINEERING. 


more  of  the  rain-fall  than  the  main  or  intercepting  sewers  into 
which  they  debouch,  the  excess  (which  is  extremely  diluted 
sewage),  flowing  off  through  the  storm-overflows  to  the  natural 
outlet.  Often  intercepting  sewers,  as  in  London,  run  for  miles 
out  of  the  city,  and  the  expense  of  carrying  all  the  storm-waters 
through  a closed  conduit  for  such  distances  would  be  something 
enormous,  so  that  the  greater  part  had  best  be  discharged  into 
the  nearest  water-course  at  certain  convenient  points. 

Mr.  Adams  proposes  a formula  to  drain  the  rain-fall  of  one 
inch  an  hour,  supposed  to  run  off  in  two  hours,  which  gives  the 
following  diameters  of  circular  sewers  in  inches  (Adams’  “ Sewers 
and  Drains,”  p.  62): 


Acres  Drained 

43 

75 

135 

308 

630 

1,117 

A,  iC 

1,925 

Fall  1-480 

Diameter,  inches 

27.6 

33.1 

40.2 

52.9 

67.2 

81.3 

97.4 

Acres  Drained 

50 

87 

155 

355 

735 

1,318 

2,225 

Fall  1-240 

Diameter,  inches 

25.7 

31 

37.5 

49.5 

63. 

76.5 

91.1 

Acres  Drained 

63 

113 

203 

460 

950 

1,692 

2,875 

Fall  1-160 

Diameter,  inches 

26. 

'31.5 

38.3 

50.4 

64.2 

77.8 

92.8 

Acres  Drained 

78 

143 

257 

590 

1,200 

2,180 

3,700 

Fall  1-120 

Diameter,  inches 

26.6 

32.5 

39.6 

52.2 

66.1 

80.7 

96.2 

Acres  Drained 

90 

165 

295 

670 

1,385 

2,486 

4,225 

Fall  1-80 

Diameter,  inches 

26. 

31.9 

38.7 

50.9 

64.3 

78.8 

94. 

Acres  Drained 

115 

182 

318 

730 

1,500 

2,675 

4,550 

Fall  1-60 

Diameter,  inches 

27. 

31.4 

37.8 

49.9 

63.5 

77. 

91.3 

Mr.  Rudolph  Heriug,  C.  E.,  proposes  a modification  of  a 
German  formula,  in  which  the  effect  of  the  inclination  of  the 
surface  and  total  area  drained  is  included  as  well  as  the  nature 
of  the  surface,  but  it  is  not  necessary  to  give  it  here,  as  its  con- 
sideration belongs  more  properly  to  the  professional. 

Relative  Amounts  of  Rain-fall  and  House  Sewage 
Proper. — We  have  seen  that  a rain-fall  of  1 inch  per  hour,  to 


WATER  SEWERAGE. 


53 


ran  off  in  two  hours,  gives  J cubic  foot  or  3.74  gallons  per  sec- 
ond for  every  acre.  To  show  its  ratio  to  the  sewage  proper,  take 
50  persons  to  the  acre,  using  75  gallons  of  water  per  day — a 
large  estimate — or  3,750  gallons  per  24  hours.  Let  us  take  one- 
half  of  this  as  flowing  off  in  8 hours,  i.  e.,  1,875  gallons  in  8 
hours,  or  0.65  gallons  per  acre  per  second  of  sewage  to  3.74  gal- 
lons of  storm- water,  or  in  the  ratio  of  1 to  58,  say.  With  100 
persons  to  the  acre,  this  ratio  will  be  as  1 to  29.  When  it  is 
remembered  that  scarcely  of  the  water  supply  is  human  sew- 
age, we  see  the  very  small  proportion  of  the  human  sewage  to 
the  total  water  to  be  carried  off  in  times  of  heavy  rain-falls, 
where  all  of  the  latter  is  admitted  to  the  sewers.  We  can  like- 
wise gain  some  idea  of  the  very  great  decrease  in  the  size,  and 
hence  of  the  cost  of  main  sewers  where  all  storm-water  is  ex- 
cluded over  sewers  of  ^The  combined  system that  admit  storm- 
waters. 

The  house  drainage  system  is,  of  course,  nearly  the  same  as  to 
cost  in  either  case,  so  that  the  difference  in  cost  is  by  no  means 
in  direct  proportion  to  the  size  of  the  main  sewers. 

From  what  has  been  said,  it  is  now  apparent  that  towns  or 
cities  contemplating  water-sewerage  have  first  to  decide  how 
much  storm-water  must  be  admitted  to  the  sewers,  and  it  is  ad- 
visable for  the  tax-payers  to  form  an  intelligent  opinion  as  to  the 
relative  merits  of  the  combined  and  the  separate  systems,  for 
engineers  will  be  found  in  many  instances  to  disagree  as  to  the 
proper  system  to  introduce. 

Combined  versus  Separate  Systems. — By  the  combined 
system  is  meant  a net-work  of  sewers  sufficient  for  the  removal 
of  alf  or  part  of  the  storm-waters,  in  addition  to  the  sewage, 
with  inlets  for  its  reception  along  the  streets  as  well  as  in  the 
yards  and  houses.  In  the  separate  system  the  storm -waters  are 
either  allowed  to  run  over  the  surface,  along  natural  or  artificial 
channels  to  the  natural  outlets,  or  a separate  system  of  sewers  is 
designed  to  carry  off  the  storm-waters  alone,  the  sewage  proper, 
with  possibly  some  rain-water  from  roofs  and  yards,  being  carried 
in  a line  of  pipes  to  any  desirable  outlet. 


54 


SANITARY  ENGINEERING. 


The  small  amount  of  rain-water  admitted  from  roofs  and  yards 
sometimes  is  for  the  purpose  of  scouring  out  the  sewers,  and  is 
generally  necessary  to  flush  the  sewers  in  time  of  rain-fall,  unless 
a special  flush-tank  is  put  at  the  head  of  each  branch  sewer,  which 
receives  a small,  steady  stream  of  water  from  the  water  supply, 
and,  when  full,  is  automatically  emptied,  thus  driving  a large 
quantity  of  water  suddenly  through  the  pipes  and  carrying  away 
any  deposits  that  may  have  occurred  from  too  small  a flow  or  too 
gentle  an  inclination  in  the  pipes. 

A system  of  small  pipe  sewers,  admitting  not  a (hop  of  rain- 
water, and  flushed  automatically  daily  with  Field’s  flush-tanks, 
and  ventilated  through  the  house  soil-pipes,  which  are  extended 
without  a trap  above  the  roof,  has  been  introduced  with  success 
at  Memphis  by  Mr.  Geo.  E.  Waring;  Jr.,  and  the  system  is  known 
as  the  “ Waring  system.”  It  is  stated  that  “the  estimated  cost 
of  this  system  there,  was  only  about  one-tenth  of  that  of  a com- 
plete storm- water  system,  as  ordinarily  constructed.” 

It  is  necessarily,  in  first  cost,  the  very  cheapest  system  that 
can  be  devised,  besides  being  in  the  line  of  simplicity  and  further 
placing  the  main  details  of  the  house  drainage,  from  the  start, 
in  the  hands  of  the  town  authorities.  Again,  where  the  sewage 
has  to  be  carried  to  some  distant  point  to  be  treated  by  filtration 
or  otherwise,  before  the  purified  effluent  is  allowed  to  go  into  the 
streams,  it  is  evident  how  much  cheaper  the  comparatively  small 
sewer  needed  is,  and  how  much  less  the  cost  of  pumping  the  rel- 
atively small  amount  of  sewage  into  the  settling  tanks,  and  the 
cost  of  subsequent  treatment  over  that  pertaining  to  the  combined 
system. 

In  towns,  and  some  cities,  the  discharge  of  storm- waters  oyer 
the  surface  may  do  but  little  or  no  damage,  and,  in  fact,  is  very 
efficient  as  a cleansing  agent;  but  certain  localities,  especially  in 
the  larger  cities,  require  storm-sewers,  for  the  flow  in  the  gutters 
may  become  a torrent  where  the  grades  are  long  and  steep,  and 
thus  travel  may  be  impeded  very  seriously,  and  damage  done  to 
streets  and  cellars. 


WATER  SEWERAGE. 


65 


It  is  urged  for  the  separate  system,  in  this  case,  that  a distinct 
set  of  sewers  to  convey  away  the  rain-water  may  be  put  in,  where 
necessary,  at  a much  less  depth  than  is  required  for  the  sewers 
proper,  and  that  they  can  discharge  into  the  nearest  stream  (thus 
giving  it  its  natural  how),  and  can  thus  be  made  shorter  than  the 
sewage  conduit,  which  is  often  carried  a considerable  distance  to 
the  outlet',  Where  the  city  is  well  cleaned  by  carting  away  the 
refuse  from  streets  and  yards  daily,  the  storm-waters  will  not 
become  too  impure,  in  their  course  towards  the  stream,  to  seri- 
ously contaminate  it.  Again,  where  grades  are  very  flat,  storm- 
sewers  may  be  needed  in  localities  where  stagnant  pools  of  water 
may  collect,  and  thus  prove  a nuisance.  In  so  large  a place  as 
Mem[)his  (60,000  inhabitants,  about),  there  are  no  storm-sewers, 
and  no  inconvenience  has  been  experienced.  Even  in  Baltimore 
the  small  pipe  system  has  been  proposed,  supplemented  by  storm- 
sewers  where  the  locality  demands  them.  There  is  probably  no 
town  in  North  Carolina  that  suffers  serious  inconvenience  from 
storm-waters  passing  over  the  surface — at  least,  over  the  greater 
part  of  its  area;  so  that,  from  this  consideration  alone,  the  com- 
bined system  could  not'  be  insisted  on  for  this  State,  with  the 
present  size  of  the  cities.  And  yet  this  one  question,  of  the 
proper  disposal  of  storm-waters,  is  the  chief  argument  used  for 
the  use  of  the  large  sewers  of  the  combined  system.  Nearly 
every  other  argument  i^  in  favor  of  the  small  sewers  of  the  sep- 
arate system. 

The  combined  sewer,  even  when  egg-shaped,  entails  deposits 
in  time  of  droughts.  The  walls  are  covered  with  slime  and 
fungous  growths  and  the  thin  film  of  sewage  cannot  carry  for- 
ward the  filth  as  readily  as  the  small  pipe  sewers  do  with  the 
same  flow,  especially  when  thoroughly  flushed  daily  by  the 
automatic  flush-tanks  at  the  head  of  each  branch  sewer. 

Therein  lies  the  chief  merit  of  the  small  pipe  sewer — no  stag- 
nation and  consequently  no  “sewer  gas”  of  the  poisonous  type 
generated  from  decaying  filth,  that  often  in  the  large  sewers 
sticks  to  the  sides  until  a copious  rain  falls  and  flushes  out  the 
entire  sewer. 


56 


SANITARY  ENGINEERING. 


Without  the  fiiish-tauk  to  clear  away  all  obstructions,  at  least 
once  in  24  hours,  the  small  pipes  might  be  found  more  harmful 
than  larger  ones  because  of  the  greater  dilution  of  the  contained 
gases  in  the  latter. 

The  large  sewers  are  generally  ventilated  through  openings 
(man-holes)  in  the  streets  every  few  hundred  feet,  and  it  is 
advisable  to  have  them  for  the  small  sewers  likewise  to  assist 
in  cleaning  out  any  accidental  obstruction  or  matter  that  the 
ordinary  daily  flushing  fails  to  remove. 

It  is,  of  course,  an  open  question  whether  the  separate  sewers 
should  be  mainly  ventilated  through  the  house-drains  as  Colonel 
Waring  proposes.  With  clean  pipes,  truly  laid  and  daily  flushed 
full,  there  should  be  no  deposit,  the  sewage  is  rapidly  carried 
out  and  the  sewer  air  can  be  safely  passed  out  through  the  house- 
drains  above  the  houses  to  be  borne  away  by  winds,  provided  the 
connections  to  the  house-drain  from  the  closets,  baths,  &c.,  in 
the  rooms  are  always  efficiently  trapped,  so  that  the  sewer  air 
does  not  pass  into  the  rooms.  The  system  thus  requires  careful 
attention. 

The  system  recommended  by  the  great  majority  of  engineers 
requires  a disconnecting  trap  outside  the  house,  which  cuts  off  the 
air  from  the  sewers,  which  thus  have  to  be  entirely  ventilated 
through  expensive  man-holes  opening  at  the  level  of  the  street. 
In  fact  the  combined  sewers  are  probably  too  large  to  be  pro- 
perly ventilated  through  the  house-drains. 

In  the  separate  system,  as  proposed  by  Mr.  Waring,  a 4-inch 
house-drain  connects  with  a 6-inch  branch  sewer, and  this  in  turn 
with  other  sewers  leading  towards  the  main  outlet  sewer,  the 
sizes  being  increased  gradually  to  allow  for  running  half  full  at 
the  time  of  greatest  flow.  The  main  outlet  sewer  at  Menifdiis 
is  only  20  inches  in  diameter,  and  of  course  diminishes  in  size 
towards  its  upper  end. 

In  very  large  cities,  combined  sewers  have  almost  invariably 
been  built,  carrying  ofl‘a  certain  part  of  the  storm-waters,  which 
are  found  to  cause  too  serious  a nuisance  to  be  left  to  take  care 
of  ihemselves.  The  storm-waters  flow  into  trapped  openings  at 


WATER  SEWERAGE. 


57 


the  corners  of  streets,  which  traps  thus  accumulate  filth  washed 
from  the  streets,  and  have  to  be  cleaned  by  hand.  This  mass  is 
often  of  an  olFensive  character,  particularly  after  decom[)osition 
sets  in. 

Indeed,  chemical  analysis  shows,  in  large  cities,  that  the  storm- 
waters wash  away  so  much  filth  as  to  render  the  water  as  impure 
as  the  sewage,  particularly  that  which  first  enters  the  sewers. 

There  is  an  objection,  too,  against  the  “separate  system,^’  in 
the  two  sets  of  sewer  pipes  (where  needed),  as  against  one  set  in 
the  combined  system,  and  this  may  become  serious  in  a densely 
populated  part  of  a city  where  innumerable  pipes  of  all  kinds 
are  laid,  particularly  as  the  drainage  pipes  must  be  laid  with  a 
fall. 

Cost  of  Water  Sewerage  by  the  two  methods. — To 
give  some  idea  of  the  relative  cost  of  the  two  systems,  we  shall 
quote  some  figures  from  a well-known  engineer,  Mr.  O.  Chanute, 
taken  from  an  address  delivered  before  the  St.  Louis  Engineers’ 
Club  and  reprinted  in  “Engineering  News”  for  May  3d,  1884: 

“The  cost  of  the  combined  system  in  St.  Louis  has  been 
|30,416  a mile.  In  Brooklyn,  N.  Y.,  it  has  been  |25,600  a 
mile,  and  the  cleaning  costs  $133  a mile  yearly.  In  Providence, 
R.  I.,  the  first  cost  has  been  $34,550  a mile,  and  the  cleaning 
cost  $282  per  mile  annually,  while  in  Memphis  the  cost  has  been 
$6,875  a mile,  and  the  sewers  are  cleaned  and  repaired  at  a cost 
of  about  $70  a mile  a year.” 

“ When  Memphis,  fever-stricken  and  ruined,  turned  to  sanitary 
engineers  for  advice,  the  sewer-builders  of  the  combined  school 
proposed  several  plans,  varying  in  cost  from  $800,000  to  over 
$2,225,000,  depending  upon  the  amount  of  storm-water  to  be 
accommodated. 

Mr.  Waring,  however,  put  in  about  18  miles  on  the  separate 
system  in  1880  at  a cost  of  $137,000,  and  the  city  authorities 
have  since  added  about  22  miles  more,  at  an  additional  cost  of 
about  $138,000,  thus  making  a total  cost  of  $275,000  for  some 
40  miles  of  sewers  at  the  close  of  1883,  which  are  said  to  drain 
even  more  territory  than  was  contemplated  in  the  estimate  for 
combined  sewers.” 


58 


SANITARY  ENGINEERING. 


It  is  not  pretended  that  the  storm-waters,  running  over  the 
surface,  have  proved  a nuisance  at  Memphis,  Mr.  Chanute  con- 
tinues : 

■^‘The  se'parate  system  of  Leavenworth,  Kansas,  now  (1884) 
approaching  completion,  has  cost  less  than  $10^000  a mile,  or,  to 
give  it  in  the  way  in  which  we  pay  our  sewer  assessments,  it  has 
cost  44J  cents  a square  (of  100  square  feet)  for  the  house-drain- 
age proper,  and,  including  the  outlets,  only  65J  cents  a square; 
while  the  combined  system  cif  Kansas  City  has  cost  to  December 
31st,  1883,  some  $2.10  a square.’^ 

^^Mr.  Latrobe’s  estimate  for  a separate  system  for  Baltimore 
also  shows  a cost  of  about  $10,000  a mile.’^ 

In  conclusion,  on  this  subject  of  the  combined  versus  the  sepa- 
rate system,  we  can  only  say  that  each  town  must  receive  a spe- 
cial study,  as  to  its  topography,  damage  to  be  feared  from  storm- 
waters and  final  disposal  of  sewage  before  the  proper  system  can 
be  arrived  at;  but  it  can  probably  be  safely  said  that  it  will  be 
many  years  before  any  town  in  North  Carolina  need  think  of 
incurring  the  extra  cost  of  the  combined  system  of  sewers,  and 
that  the  separate  system,  with  perhaps  a few  storm-sewers,  will 
answer  all  present  requirements. 

Sewerage  of  Low-lying  Localities. — Mr.  Waring  signi- 
ficantly remarks  (Paper  on  ^‘The  Sewering  and  Draining  of 
Cities),  there  is  one  point  connected  with  the  drainage  of  towns 
which  is  not  sufficiently  appreciated,  especially  in  this  country — 
that  is,  that  it  is  easy  and  cheap  to  secure  a deep  outlet  in  low 
land,  and  to  deliver  sewage  at  a considerable  elevation  for  agri- 
cultural treatment,  by  artificial  pumping. 

^‘The  average  cost  of  pumping  for  water-works  is  about  nine 
cents  per  foot  of  elevation  for  each  million  gallons  raised.  On 
this  basis  t\ys  cost  of  raising  the  sewage  of  a town  of  10,000 
inhabitants,  supposing  every  three  persons  of  the  population  to 
contribute  one  hundred  gallons  per  day  to  the  flow,  would  be 
about  three  cents  per  day  for  each  foot?  of  elevation.’^ 

Similarly  the  rain-fall  can  be  provided  for  in  connection  with 
deep  subsoil  drainage  in  all  damp  or  naturally  overflowed  local- 


WATER  SEWERAGE. 


59 


ities,  as  New  Orleans.  In  fact,  wherever  delivering  the  sewage 
into  the  stream  or  body  of  water  near  at  hand  means  contamina- 
tion of  the  town,  pumping  will  have  to  be  resorted  to.  Boston 
has  secured  deep  drainage  by  such  means  and  in  addition  re- 
moves her  sewage  to  such  a distance  that  the  return  tide  does  not 
bring  it  back  to  the  city. 

Subsoil  Drainage. — If  there  is  but  one  sewer  system,  then 
the  subsoil  must  be  drained  by  small  pipes,  simply  butted  to- 
gether at  the  ends,  so  that  the  subsoil  water  can  enter.  The  pipes 
must  be  placed  on  top  of  the  sewer  pipe  to  prevent  any  infiltra- 
tion from  the  sewer,  which  often  happens  if  they  are  placed 
below  the  sewer.  This  subsoil  drainage  is  especially  necessary 
in  a retentive  soil,  to  render  the  soil  porous,  so  that  it  can  more 
effectually  do  its  work  of  oxidation  on  any  gases  that  may  pass 
through  the  sewer. 

The  latter  should  be  rendered  as  impervious  as  possible,  for 
leakage  through  bad  sewers  into  the  ground  soon  saturates  it 
with  the  vilest  poison,  that  invariably  produces  harm  as  soon  as 
it  can  find  an  outlet  to  the  outer  air. 

Form,  Inclination  and  Ventilation  of  Sewers. — Small 
circular  sewers  can  be  made  of  earthenware  pipe,  larger  ones* of 
brick  in  cement  or  of  concrete,  and  egg-shaped,  to  give  a greater 
velocity  to  a small  flow.  Main  sewers  should  not  be  laid  af 
greater  inclinations  than  cause  a velocity  of  six  feet  per  second, 
if  possible,  to  avoid  the  cutting  out  of  the  bottom  of  the  sewer 
by  grit  and  other  solids.  The  location  of  the  main  outlet  sewer 
determines,  to  a great  extent,  the  positions  of  the  other  sewers, 
and  should  receive  special  study.  House-drains  are  generally 
trapped  and  ventilated  between  the  house  and  sewer.  The  main 
sewers  should  be  ventilated  by  direct  communication  with  the 
external  air,  at  least  every  100  yards.  This  prevents  that  partial 
and  noxious  decomposition  which  occurs  in  close  places  having 
a limited  amount  of  air. 

‘Hn  fully  ventilated  sewers,  the  sewer  air  is  generally  purer 
than  that  of  some  stables,  or  even  in  a crowded  public  room.^^ 


60 


SANITARY  ENGINEERING. 


It  is  always  advisable  to  place  the  man-holes  at  each  curve  or 
change  of  grade  of  the  sewers,  so  that  one  can  see  down  the  sew- 
ers from  man-hole  to  man-hole,  especially  for  small  sewers,  where 
scrapers  have  to  be  pulled  through  to  clear  away  any  deposits. 

House-drainage. — The  proper*  treatment  of  this  subject, 
like  some  others  that  have  only  been  briefly  touched  upon,  would 
require  a volume  in  itself,  at  least  to  consider  all  the  various 
designs  and  fixtures  that  have  been  proposed ; but  the  essential 
elements  of  house-drainage  can  be  gained  from  a consideration 
of  the  subjoined  diagram,  taken  by  permission  of  the  publisher 
(D.  Van  Nostrand,  N.  Y.),  from  the  excellent  little  manual  by 
Wm.  Paul  Gerhard,  civil  sanitary  engineer,  entitled  ^‘House- 
drainage  and  Sanitary  Plumbing,’’  to  which  the  reader  is 
referred  for  further  information. 

The  figure  represents  a section  through  a dwelling-house,  in 
which  C is  the  4-inch  house-drain  connecting  with  the  sewer  (not 
shown)  that  carries  ofi‘  all  wastes  and  liquids  from  the  house. 

D is  the  running-trap  on  the  main  drain  to' disconnect  the 
house  from  the  sewer. 

In  the  ^‘Waring  system  ” this  trap  is  left  out,  so  that  the  house- 
drain  extended  as  shown,  full  fore,  above  the  roof,  serves  to  ven- 
tilate the  sewers,  reliance  being  placed  entirely  in  the  traps  to 
room  fixtures  to  exclude  the  sewer  air  from  the  rooms.  In  Eng- 
lish practice  it  is  recommended  to  have  two  such  traps  as  that 
shown  at  D outside  the  house  with  an  open  gulley  between  them, 
to  permit  the  discharge  of  sewer  air  if  the  first  trap  is  forced 
from  too  great  back  pressure  in  the  sewer,  as  well  as  for  pur- 
poses of  cleaning. 

Such  open  traps  are  liable  to  freezing  in  Northern  latitude,  but 
are  advisable  in  our  Southern  States,  as  being  an  additional  secu- 
rity against  the  admission  of  sewer  air.  Their  use  necessarily 
entails  the  ventilation  of  the  sewers  through  man-holes.  The 
Waring  plan  is  simpler  and  cheaper,  and  it  would  seem  that  if 
experience  shows  that  the  sewer  air,  from  the  daily  flushing, 
remains  purer  than  that  of  the  house-drains,  and  that  obstruc- 
tions are  quickly  got  rid  of,  that  the  plan  is  to  be  recommended 
for  the  small  pipe  sewers*. 


WATER  SEWERAGE. 


61 


p]  is  a V branch  closed  with  a screw  for  cleaning.  F is  the 
fresh  air  pipe,  to  permit  of  a constant  circulation  of  air  in  the 
house-drain  inside  of  the  house,  to  oxidize  the  foul  organic  mat- 
ter clinging  to  the  pipes.  The  current  is  generally  from  the 
fresh  air  inlet  up,  through  the  roof,  as  the  house-pipe  is  warmer 
as  a rule,  except  perhaps  some  days  in  summer. 

Another  reason  in  favor  of  this  fresh  air  inlet,  when  the  drain 
has  been  trapped  outside  ^the  house,  is  that  without  it,  water  dis- 
charged through  any  fixture  into  the  house-drain,  forces  a certain 
amount  of  air  before  it  which  may,  in  turn,  force  some  trap  and 
thus  send  a puff  of  sewer  air  into  the  living-rooms. 

In  the  Waring  system  this  fresh  air  inlet  is  left  out. 

It  is  evident  that  if  the  house-drain  discharges  into  a cess-pool 
or  flush-tank,  that  the  trap  D and  inlet  F should  not  be  omitted. 

G is  the  4-inch  house-drain,  laid  with  a fall  and  supported 
from  the  ground  to  prevent  settling  and  opening  of  the  joints. 
H H are  the  4-inch  soil  pipes,  protected  at  top  by  wire-baskets. 
Both  G and  H should  be  of  cast-iron  with  well  caulked  lead 
joints.  The  other  pipes  are  often  of  lead,  though  in  the  system 
carried  out  by  the  Durham  House-drainage  Company,  all  pipes 
are  of  wrought-iron,  with  special  screw  joints  that  are  perfectly 
light.  Such  a system  is  supported  from  the  ground,  so  that  it  is 
not  liable  to  open  joints  from  settlement  of  walls  or  floors,  the 
pipes  being  of  sufficient  strength  to  withstand  the  strain.  As  a 
fact,  cast-iron  pipe  is  not  of  uniform  thickness  or  strength,  whilst 
lap-welded  wrought-iron  pipe  can  be  so  obtained,  so  that  this 
Durham  system  is  to  be  regarded  as  superior  to  the  ordinary 
method  of  plumbing,  particularly  where  much  lead  pipe  is  used; 
for  lead  is  liable  to  sag  and  split  open,  to  be  corroded  by  sewer 
gas  on  the  upper  side,  to  have  nails  driven  into  it ; and,  to  be 
eaten  into  by  rats.  Still  lead  is  almost  universally  used  for  con- 
nections and  is  generally  satisfactory. 

J is  a refrigerator;  K,  a water-tank  supplied  from  the  street 
pressure.  Its  overflow-pipe  L is  trapped  by  an  S trap  with  deep 
seal,  and  emptying  into  the  gutter  of  the  roof.  The  blow-off 
from  tank  delivers  over  the  kitchen  sink. 


62 


SANITARY  ENGINEERING. 


M M are  small  cisterns  for  flushing  the  water-closets  and  slop- 
hopper  only.  Where  fixtures  are  flushed  by  pipes  from  the  street 
pressure,  it  sometimes  happens  that  if  a lower  cock  is  opened,, 
that  the  upper  cock  (which  we  suppose  open  too)  will,  for  the 
time,  cease  to  flow  and  in  fact  suck  ^n  the  air  of  the  fixture  into 
the  water-supply,  thus  poisoning  all  the  drinking  water. 

O O are  wash-bowls  with  IJ-inch  waste-pipes  and  overflow- 
pipes  of  lead,  trapped  by  anti-siphoning  or  mechanical  traps,  and 
delivering  into  4x  2 Y branches  of  the  soil-pipes. 

P is  a pantry  sink,  trapped  as  above. 

Q are  slate,  cement  stone,  soapstone,  or  ceramic  wash-tubs, 
with  IJ-inch  waste-pipe,  trapped  as  before. 

T is  a bath-tub,  of  enameled  iron  or  heavy  planished  copper, 
or  of  porcelain.  It  is  provided  with  a standing-waste  and  trap- 
ped by  a mechanical  trap. 

T'  is  a hip-bath,  trapped  by  a vented  S trap. 

V is  a 2-inch  air-pipe  to  prevent  the  siphonage  of  the  water- 
closet  traps. 

It  is  seen,  from  the  figure,  that  vent-pipes  from  the  top-bend 
of  traps  enter  this  pipe  V,  thus  tending  to  prevent  any  siphon- 
age  action  in  such  bends. 

It  is  enlarged  to  4 inches  through  the  roof.  The  water-closet 
trap  at  the  right  of  the  bath-tub  is  not  shown  with  a vent,  be- 
cause the  water-closet  is  of  the  improved  short  hopper  type^  hold- 
ing water  to  the  depth  of  six  inches  in  the  bowl,  which  seal 
could  never  be  broken  by  siphonage  or  capillary  attraction.’’ 

Siphonage  may  occur  in  traps  with  small  depth  of  seal,  by  the 
momentum  of  the  flushing  water  suddenly  discharged  into  the 
trap,  filling  the  upper  bend  and  thus  starting  a siphon  action, 
which  nearly  empties  the  trap  and  allows  sewer  air  to  enter.  The 
seal  may  be  broken  by  siphonage  likewise,  by  the  discharge  of  a 
large  quantity  of  water  into  some  other  fixture  connecting  with 
the  same  soil-pipe,  from  the  tendency  to  create  a partial  vacuum ; 
particularly  if  the  second  fixture  discharges  through  the  same 
pipe,  into  the  soil-pipe,  as  the  first,  a method  to  be  avoided  if 
possible. 


WATER  SEWERAGE. 


63 


64 


SANITARY  ENGINEERING. 


The  vent-pipes  mentioned  are  generally  as  afegnard  against 
siphonage  from  the  causes  enumerated,  though  they  cause  in- 
creased evaporation  from  water-seals,  and  thus  prove  a draw- 
back when  fixtures  are  unused  for  some  time. 

In  fact,  it  is  absolutely  necessary  to  run  water  into  fixtures 
periodically  to  prevent  sewer  air  from  entering  rooms,  particu- 
larly when  unused  and  unventilated. 

The  soil-pi {)es  H H extended  through  the  roof  and  open  at 
top  effectually  prevent  traps  being  forced  by  back  pressure  from 
the  sewers. 

In  addition  to  the  loss  of  water-seal  through  siphonage,  eva- 
poration and  back  pressure,  capillary  attraction  may  be  added; 
for  if  threads  or  hairs  extend  from  the  water  in  the  trap  over 
the  bend,  the  water  may  be  drawm  off*  along  the  filaments  by 
capillary  attraction. 

A deep  seal  is  a protection  against  all  the  causes  named,  though 
nothing  can  take  the  place  of  continual  supervision.  Eternal 
vigilance  alone  is  the  price  of  health.  It  must  be  borne  in  mind 
too,  that  the  water  in  traps  absorbs  sewer-gas  and  passes  some  of 
its  constituents  into  the  room.  It  is  true  that  the  amount  is  very 
small  and  considered  harmless,  for  experiment  seems  to  indicate 
that  germs,  even  if  contained  in  the  water  of  traps,  are  not  libe- 
rated from  it,  as  was  hitherto  supposed,  unless  the  water  is  vio- 
lently agitated’’;  still  it  is  in  every  way  desirable  and  on  the  side 
of  safety  to  change  the  water  of  traps  every  few  days,  and  keep 
down  any  slight  odor  that  might  arise,  so  that  the  air  of  rooms 
is  always  sweet  and  pure. 

The  water-closets,  in  the  figure,  W W W,  are  of  the  long  and 
short  hopper  and  washout  kinels,  without  any  mechanical  device 
(as  in  the  pan,  valve  and  plunger  closets)  to  get  out  of  order  and 
become  foul.  It  is  true  that  these  closets  become  foul  at  times, 
but  then  they  can  be  readily  cleaned,  which  cannot  be  said  of  the 
mechanical  closets,  whose  foul  [)arts  are  not  so  easily  got  at.  The 
above  closets  are  flushed  from  the  special  cisterns  M M M. 

X X is  the  rain-leader  delivering  the  water  into  the  running- 
trap  of  the  house-drain. 


WATER  SEWERAGE. 


65 


Y is  the  blow-off'  from  the  boiler,  which  wastes  into  a Y 
branch  of  the  iron  drain  in  the  cellar. 

Drainage  of  the  Foundation. — The  subsoil- water  below 
the  house  is  kept  at  a certain  depth  by  laying  small  IJ-'ach  tiles 
inside  of  the  foundation  walls  to  a little  more  than  tiie  required 
depth,  say  2 or  3 feet,  d'hese  pipes  connect  with  the  joain  drain, 
B in  the  figure,  which  discharges  into  a gravel-trap  A,  with  a 
water-seal  to  prevent  sewer-gas  from  entering  the  drain  tiles  and 
thus  poisoning  the  ground  under  the  house,  in  case  a connection  is 
made  with  the  sewer.  For  the  same  reason  the  outlet  pipe  from 
the  trap  A should  bend  downwards  into  the  water.  Often  this 
trap  is  made  of  large  pipe  which  extends  vertically  up  to  the 
surface,  and  is  protected  by  a grading,  in  order  that  the  water-seal 
may  be  periodically  inspected  and  cleaned. 

The  best  practice  is  to  lay  subsoil  (trains  along  side  the  sewers 
into  which  drains  like  B discharge  directly  without  the  interven- 
tion of  a trap,  as  no  sewer-gas  need  then  be  feared. 

The  tile  drains  are  laid  with  open  joints,  around  which  tarred 
paper  or  cloth  may  be  WTapped  to  prevent  the  entrance  of  dirt. 

In  a country  house  fhe  trap  A is  not  needed,  as  the  drain  can 
generally  be  made  to  discharge  at  the  surface  at  some  lower  level 
than  the  house  is  situated  on. 

In  such  case  the  mouth  of  the  drain  should  be  protected  from 
wash  by  a foundation  of  stones  properly  laid  and  a grating  of 
iron  or  earthenware  should  be  placed  in  the  mouth  to  prevent 
vermin  from  entering  and  obstructing  the  drain  by  building 
nests  within  -it. 

The  roots  of  trees  often  enter  drains  through  open  joints  and 
choke  them  up.  Cementing  the  joints  near  the  trees  with 
asphalt  must  then  be  resorted  to  or  the  tree  must  be  cut  down. 

In  place  of  the  tile  drains  mentioned,  broken  stone  thrown  to 
the  bottom  of  the  trench  to  a certain  depth  and  covered  up  with 
earth,  also  box  drains  of  wood,  and  pole  drains,  may  be  more 
cheaply  constructed,  but  they  cannot  be  regarded  as  at  all  per- 
manent, as  the  broken  stone  drains  finally  fill  up  with  earth  and 
the  wooden  drains  decay  after  a number  of  years. 

5 


66 


SANITARY  ENGINEERINa. 


Dampness  of  wares  and  cellars. — To  prevent  daaipness 
of  walls  and  cellars  below  the  ground-level  an  imj)ervious  or 
^^damp  course  must  be  used. 

For  cellars  a layer  of  asphalt  J inch  thick  on  top  of  the  con- 
crete floor,  covered  by  a layer  of  cement,  is  found  to  be  very  effi- 
cacious. This  layer  of  asphalt  should  be  continued  through  the 
walls  and  extended  upwards  on  the  outside  to  the  ground-level 
to  completely  shut  off  dampness  in  the  foundation  walls. 

A horizontal  layer  of  slate  in  concrete  is  often  laid  in  the  walls 
at  the  ground-level  and  effectually  cuts  off  dampness  from  below. 

The  space  immediately  around  the  walls  should  be  filled  with 
broken  stone  and  the  footing  course  of  the  walls  may  rest  upon 
broken  stone,  if  the  foundation  is  good,  otherwise  upon  concrete, 
especially  in  the  case  of  large  buildings. 

Double  walls,  with  an  air-space  between,  are  likewise  used  to 
prevent  dampness  whether  from  the  soil  or  the  atmosphere. 

By  the  proper  drainage  of  the  subsoil  and  the  use  of  damp 
courses  all  through  the  foundations,  we  not  only  ensure  dryness 
— a very  important  thing  to  health — but  also  prevent  the  en- 
trance of  sewer-air  or  poisonous  gases  thrown  off  by  decompos- 
ing animal  or  vegetable  matter  in  the  subsoil,  often  carelessly 
placed  against  the  walls.  Prof.  Renk  finds  ‘Hhat  the  draught 
or  current  is  from  the  ground  into  the  house  for  the  greater  part 
of'  the  year  and  that  it  brings  with  it  particles  of  whatever 
injurious  matter  the  soil  may  contain.^’  ^^This  ground-air  is 
kept  in  continual  movement  by  the  state  of  the  winds  and  the 
atmosphere.’’ 

For  further  information  on  this  subject  of  foundations,  see  a 
recent  publication,  ‘‘Healthy  Foundations  for  Houses,”  by 
Glenn  Brown,  D.  Van  Nostrand,  N.  Y.,  publisher. 

Cess-pools. — rin  cities  where  water  sewerage  has  not  yet  been 
introduced,  the  abomination  called  the  cess-pool  is  used  to  receive 
the  filth  of  the  houses.  These  cess-pools  are  of  two  kinds,  the 
leaching  and  the  tight  cess-pools.  Both  are  receptacles  built  of 
brick,  say  of  5 to  10  feet  diameter  and  5 or  6 feet  high  and 
dome-shaped,  surrounded  with  earth,  with  the  soil-pipe  entering 


WATER  SEWERAGE. 


67 


OD  the  side,  and  preferably,  with  two  ventilating  pipesextending 
from  the  top  of  the  dome  and  near  the  sewer  entrance  respect- 
ively, some  10  feet  above  ground  to  carry  off  impure  gases  by 
the  current  induced  and  to  prevent  undue  pressure  in  the  cess- 
pool from  the  gases  formed.  In  the  leaching  cess-pool  the  brick- 
walls  are  {)orous,  so  that  the  sewage  can  soak  through  them  into 
the  ground,  where  it  remains  to  poison  the  ground-water  or  to 
decompose  and  gradually  find  its  way  to  the  surface  as  gas,  where 
a healthier  decomposition  may  render  it  harmless. 

Nothing  can  he  worse  than  this  poisoning  of  the  ground  if 
water  is  taken  from  wells  in  the  vicinity,  for  sooner  or  later,  the 
sewage  must  reach  them;  besides,  the  ground-air  around  and 
under  a house  should  be  as  pure  as  possible,  for  it  is  the  air  we 
breathe;  lasily,  the  leaching  cess-pool  permanently  pollutes  the 
soil,  no  matter  if  a better  system  is  ultimately  introduced,  and 
thus  digging  new  trenches  or  foundations  in  such  a soil  must  be 
attended  with  deleterious  consequences. 

The  absolutely  tight  cess-pool,  with  cemented  walls,  is  a great 
improvement  over  the  leaching  cess-pool,  and  it  must  be  regarded 
as  only  a temporary  receptacle  for  filth,  which  is  to  be  pumped 
out  and  removed  outside  the  city  limits  periodically. 

The  suction-pipe  can  be  let  down  through  a hole  in  the  dome, 
left  for  that  purpose,  and  which  is  ordinarily  covered  with  a slab. 

The  tight  cess-pool  is  too  often  so  badly  made  as  to  prove  a 
leaching  cess-pool ; besides,  its  ventilation  is  generally  neglected, 
so  that  sickening  gases  issue  from  it  on  opening,  and  sometimes 
storm-waters  may  cause  it  to  overflow  back  into  the  house,  unless 
it  is  carefully  attended  to. 

These  cess-pools,  when  they  have  to  be  used,  should  be  located 
at  least  50  or  60  feet  from  the  house,  in  fact  as  far  away  as  prac- 
ticable. They  should  only  be  tolerated  as  a necessary,  though 
temporary  nuisance,  for  use  in  towns  where  water  sewerage  can- 
not be  afforded,  a system  whose  main  purpose  is  to  remove,  as 
rapidly  as  possible,  all  filth  outside  the  city  limits,  as  opposed  to 
the  system  of  storing  up  this  filth  in  cess-pools  or  in  the  ground 
for  indefinite  periods,  thus  vitiating  both  the  soil  and  the  atmos- 
phere. 


68 


SANITAEY  ENGINEERING. 


Disposition  of  Sewage. — Having  briefly  considered  some 
points  of  general  interest  in  connection  with  the  design  of  sewer- 
age works,  let  us  next  enquire  what  is  to  be  done  with  the  sew- 
age. 

The  plan  most  in  vogue  in  this  country  is  to  discharge  the 
sewage  matter  into  some  stream,  which  may  thus  be  regarded,  in 
one  sense,  as  the  continuation  of  the  sewer. 

In  the  case  of  tidal-waters,  however,  if  the  refuse  is  emptied 
near  the  city  it  floats  up  and  down  the  city  past  it,  giving  any- 
thing but  an  air  of  cleanliness  to  the  eye,  or  of  satisfaction  to 
the  nose. 

In  England,  the  law  now  ‘‘requires  that  rivers  and  streams 
are  not  to  be  polluted  by  the  admission  of  crude  sewage,  even 
from  existing  sewers.’^ 

Rawlinson  states  that  up  to  October,  1878,  “there  are  about 
87  towns,  districts,  parishes,  and  places  whose  sewage  is  disposed 
of  by  irrigation.  There  are  23  towns,  &c.,  whose  sewage  is  dis- 
posed of  by  precipitation,  treatment  with  chemicals,  and  partial 
land -filtration.  There  are  24  towns,  &c.,  whose  sewage  is  dis- 
posed of  by  ruder  and  more  imperfect  modes  of  filtration,  as 
through  charcoal,  wicker-work  and  straw.  There  are  16  towns, 
&c.,  whose  sewage  is  disposed  of  by  mechanical  subsidence  only.’^ 
The  sewage  is  first  carried  by  the  outlet  sewer  to  the  “sewer- 
farm,^^  where,  if  necessary,  it  is  pumped  into  large  tanks,  to  be 
then  treated  according  to  some  of  the  methods  given  above. 

Irrigation  and  Filtration. — The  best  method,  probably, 
is  irrigation,  or  filtration  through  a porous  soil. 

This  j)lan  might  be  carried  out  for  small  towns  by  passing  the 
sewage  at  intervals  from  large  tanks,  where  it  is  collected,  through 
hundreds  of  earthenware  pipes,  loosely  jointed,  placed  about  one 
foot  below  the  surface  of  the  ground  and  in  parallel  rows.  The 
sewage  leaks  through  the  joints  into  the  surrounding  soil,  which 
purifies  it  by  absorption  and  oxidation.  A chea[)er  method  for 
cities  consists  in  simply  passing  the  fluid  sewage  on  to  ground 
deeply  drained.  The  purified  water  runs  ofi*  in  the  drains,  and 
thence  into  the  streams. 


watp:r  sp:wp:rage. 


69 


By  distributing'  the  sewage  over  a suflficieni  extent  of  surface, 
it  is  found  that  the  soil  does  its  work  perfectly;  being  aided, 
moreover,  by  the  growing  vegetation,  taking  up  much  of  the  sew- 
age through  its  roots.  The  purification,  though,  is  principally 
due  to  the  earth,  which  has  the  property  of  absorbing  and  con- 
densing gases,  such  as  air,  &c.;  so  that  each  little  [)article  of 
earth  is  surrounded  with  condensed  oxygen,  which  acts  upon  the 
sewage  matter  the  instant  it  comes  in  contact  with  it,  and  oxidizes 
the  organic  part, — throwing  olf  some  of  it  into  the  air — not  as 
poisonous  effluvia,  which  is  the  result  of  decomposition  with  a 
limited  amount  of  oxygen,  as  in  close  drains,  but  as  harmless 
aqueous  vapor,  carbonic  acid  and  ammonia.  The  amount  of 
oxygen  absorbed  by  the  soil  is  not  large,  but  it  seems  to  be  re- 
placed as  rapidly  as  it  enters  into  combination,  and  thus  to  fur- 
nish an  indefinite  supply  to  the  matter  with  which  it  combines. 
(See  Johnson’s  ‘^How  Crops  Feed,”  pp.  218,  168,  etc.). 

It  must  then  be  distinctly  understood  that  the  putrescent  sub- 
stances are  not  simply  absorbed  (as  usually  stated)  by  the  earth  or 
charcoal,  or  other  porous  material ; but  are  chemically  changed 
— oxidized  or  burnt  up — so  that  their  objectionable  features  are 
no  longer  perceived;  the  nitrogen,  etc.,  is  thrown  off  into  the  air, 
or  passes  off  in  the  water  as  nitrates,  or  nitrites,  so  that  the  earth 
ultimately  has  about  the  same  constitution  after  its  use  in  the 
manner  indicated  as  before. 

At  Merthyr  the  effluent  water  from  the  filter-beds  was  analy- 
zed by  Dr.  Frankland,  showing  that  when  230,  500  and  1,200 
people  were  draining  on  to  them  per  acre,  the  effluent  water  was 
respectively  30,  16  and  3 or  4 times  purer  than  the  standard  of 
fair  potable  water,  so  . far  as  chemical  analysis  is  taken  as  the 
criterion. 

It  is  thus  seen  how  effectually  surface  soil,  where  there  is  plenty 
of  air,  does  its  work.  It  is  warmly  advocated  by  Geo.  E.  War- 
ing, Jr.  (see  ^‘The  Sanitary  Condition  of  Dwelling  Houses,” 
Van  Nostrand)  to  get  rid  of  all  liquid  refuse,  about  the  country 
or  town  house,  where  there  is  no  system  of  sewers,  by  passing  it 
from  a flush-tank  through  loosely-jointed  pipes,  laid  about  one 


70 


SANITARY  ENGINEERING. 


foot  below  the  surface  in  the  back  yard.  He  states  that  the  sys- 
tem has  been  found  to  work  admirably,  winter  and  summer, 
wherever  tried. 

It  may  be  stated  that  the  efforts  that  have  hitherto  been  made 
to  utilize  the  fertilizing  properties  of  sewage  have  not  been  pro- 
fitable, unless  in  .the  way  of  irrigation.  Fine  crops  have  been 
raised  on  such  sewage  farms;  so  that  where  intermittent  filtra- 
tion is  adopted,  it  is  advisable  to  combine  sewage  farming  with 
it  to  lessen  the  expense. 

The  Chemical  Processes  used  so  far  have  not  been  found 
C)  purify  the  sewage  thoroughly  by  themselves,  so  that  natural 
or  artificial  filtration  must  supplement  any  chemical  treatment. 
Besides  this  objection  to  the  chemical  method,  its  cost  and  diffi- 
culty .of  manipulating  the  accumulations  of  sewage  sludge  both 
make  against  it;  still  much  of  this  sludge  must  be  removed  in 
some  way  before  filtration  can  be  employed. 

In  seaboard  towns,  the  natural  outfall  for  the  sewage  is  the 
sea.  If  possible  the  sewage  should  be  carried  to  such  -a  distance 
as  not  to  be  brought  back  to  the  town  by  wind,  tides  or  current. 
The  same  remarks  apply  to  towns  situated  on  tidal  streams  and 
estuaries. 

Caution  to  our  Cities. — Most  of  our  large  towns  have  a 
clean  slate  for  sewerage  systems.  Let  not  a single  sewer  be  built 
until  a competent  engineer  plans  the  entire  system,  otherwise  the 
sewers  may  have  to  be  torn  up  eventually,  or  the  engineer  may 
be  considerably  embarrassed  in  his  designs. 

THE  LIEURNUR  SYSTEM. 

In  a paper  read  before  the  Austrian  Society  of  Engineers, 
Vienna  (see  Baldwin  Latham^s  “Sanitary  Engineering,’’  Am. 
ed.),  Mr.  J.  Chailly  says: 

“The  two  conditions  of  removal  without  producing  disagree- 
able odors,  and  carrying  off  the  matter  in  short  periods,  are 
almost  entirely  fulfilled  in  Lieurnur’s  Pneumatic  Sewerage  sys- 
tem, in  which  the  iron  waste-pipes,  which  are  water-tight  and 
air-tight,  are  united  to  a system  of  iron-pipes  which  run  into  a 


THE  KOCllPH)ALE  SYSTEM. 


71 


central  station,  where  the  air-piiinp  is  placed  which  pumps  all 
the  matter  into  a reservoir.  The  collection  and  sale  of  this  mat- 
ter does  not  usually  cover  the  cost  of  the  labor.  The  reports  on 
this  system  are  conflicting,  and  yet  the  majority  of  them  speak 
in  its  favor.^’ 

Mr.  C.  Norman  Bazalgette,  in  a late  |>aper  to  the  London 
Institution  of  Civil  Engineer,  says  of  this  system  from  the 
experience  gained  at  Leyden,  Amsterdam  and  Dodrecht,  that 
it  was  supplementary  to,  and  not  substitutive  of,  a water  car- 
riage system,  extremely  costly,  and  its  mechanism  w^as  extremely 
complicated  and  liable  to  get  out  of  order.  The  accumulation  of 
sewage  residium  in  the  central  reservoir,  and  its  subsequent 
decanting  into  barrels,  W'ere  operations  which  could  not  fail  to 
be  objectionable  and  offensive.  In  conclusion,  the  system — 
though  it  might  have  a partial  j)rovince  in  the  tide-locked  cities 
of  the  Hague,  where  no  system  of  sew^erage  was  available — 
should  never  be  imported  into  an  English  town.’’ 

It  would  seem  that  there  would  be  considerable  difficulty 
experienced  in  the  case  of  repairs  to  the  pipes  being  needed. 

THE  ROCHEDALE  PAIL  SYSTEM.* 

This  consists  simply  in  half-barrels  or  pails  being  placed  under 
the  seats  of  the  closed  privy  to  receive  the  fecal  discharges;  the 
pails  being  removed  about  once  a week,  after  putting  on  a her- 
metically-tight  cover,  empty  disinfected  pails  taking  their  place. 
The  matter  is  carried  out  of  the  town  at  night,  and  may  be 
spread  on  old  fields,  a slight  covering  of  dry  earth  being  used  to 
keep  down  the  smell,  or  the  matter  may  be  sold  for  manure.  It 
is  well  to  add  dry  earth,  ashes  or  charcoal  every  day  to  the  pails 
in  use,  and  moreover  to  ventilate  the  privy. 

This  system  is  an  excellent  one  for  most  of  our  towns  and 
small  cities.  Having  to  carry  the  pails  through  the  house  or 
yard  to  the  street  is  an  objection.  It  is  now  being  tried  on  a 
large  scale  in  New  Orleans,  where  the  water  system  cannot  be 
readily  used. 


*See  Appendix  II,  page  79. 


72 


SANITARY  ENGINEERING. 


All  of  our  cities  and  towns  can  introduce  this  system  with 
such  a small  outlay  of  capital,  that  it  would  seem  to  be  the  one 
just  now  to  be  most  highly  recommended  for  many  towns. 

The  corporation  should  bear  the  expenses  of  the  transporta- 
tion of  the  excrementitious  matter,  as  well  as  of  other  refuse  and 
filth  found  in  all  towns,  due  to  various  causes. 

THE  DRY  EARTH  SYSTEM. 

The  great  advantages  offered  by  the  ‘^dry  earth  closet^’  is  well  . 
known,  and  its  admirable  adaptability  to  the  sick-room. 

The  system  proposed  is  founded  on  this,  and  consists  in  the 
same  pails  used  in  the  preceding  system,  placed  in  closed  'privies^ 
on  fiy^m  and  dry  plank  or  concrete  foundation.'^  The  only  dif- 
ference is,  that  in  this  system  greater  care  is  used  in  spreading 
charcoal  or  dry  earth  over  the  night  soil,  so  as  to  burn  it  up  as 
quickly  as  possible,  and  that  the  pails  are  emptied  in  a tight 
vault  on  the  premises,  a little  earth  being  thrown  on  top  of  the 
emptied  mass  to  keep  down  odor  and  continue  the  work  of 
exodation  to  completion. 

There  appeared  an  excellent  article  on  ^‘Village  Sanitary 
Work^’  in  Scribner^  for  June,  1877,  by  George  E.  Waring,  Jr. 
The  writer  says:  ^^In  the  autumn  of  1876,  I had  brought  to 
my  house,  where  only  earth  clbsets  are  used,  two  small  cart  loads 
of  garden  earth,  dried  and  sifted.  This  was  used  repeatedly  in 
the  closets,  and  when  an  increased  quantity  was  required,  addi- 
tions were  made  of  sifted  anthracite  ashes.  The  amount  of 
material  m)w  on  hand  is  about  two  tons,  which  is  ample  to  fur- 
nish a supply  of  dry  and  decomposed  material  whenever  it  be- 
comes necessary  to  fill  the  reservoirs  of  the  closets.  The  accumu- 
lation under  the  seats  is  discharged  through  valves  into  brick 
vaults  in  the  cellar.  When  these  vaults  become  filled — about 
three  times  in  a year — their  contents,  which  are  all  thoroughly 
decomposed,  are  piled  up  in  a dry  and  ventilated  place,  with  a 
slight  covering  of  fresh  earth  to  keej)  down  any  odor  that  might 
arise.  After  a sufficient  interval  these  heaps  are  ready  lor  further 


*See  Appendix  II,  pages  78  and  79. 


THE  DEV  EARTH  SYSTEM. 


73 


use,  there  l)eii)g  no  trace  in  any  portion  of  foreign  matter  or  any 
appearance  or  odor  differing  from  that  of  an  unused  mixture  of 
earth  and  ashes.  In  this  way  the  material  has  been  used  over 
and  over  again,  at  least  ten  times,  and  there  is  no  indication  to 
the  sense*  of  any  change  in  its  condition.’’ 

The  same  earth  can  be  used  over  and  over  again,  thus  doing 
away  with  what  was  once  urged  as  the  principle  objection  to  the 
earth-closet  system — the  continual  removal  of  large  bodies  of 
earth. 

A chemical  analysis  showed  that  there  was  no  more  organic 
matter  in  the  used  earth  than  in  fresh  earth,  thus  proving  that 
in  this  case  800  pounds  of  nitrogen,  etc.,  had  gone  back  to  the 
air  in  a harmless  state,  the  solid  organic  matter  being  estimated 
at  800  pounds,  of  which  some  230  was  nitrogen. 

The  powerful  disinfecting  [iroperties  of  charcoal  are  well 
known.  When  there  is  odor  about  a dead  body,  there  is  nothing 
better  than  carbon  in  some  of  its  forms  to  destroy  it.  The  smoke 
from  burning  tar,  coffee,  dried  apples,  etc.,  have  all  been  success- 
fully tried. 

A covering  of  charcoal  will  preserve  tainted  flesh  of  any  kind  ; 
the  dog  instinctively  acts  upon  this  principle  when  he  buries  a 
bone  in  the  earth  to  make  a repast,  upon  some  days  or  weeks 
afterwards.  In  all  these  cases  it  is  not  the  charcoal  or  earth,  but 
the  oxygen  contained  in  its  pores  that  destroys  the  odors  and 
burns  up  the  substance. 

As  Mr.  Waring  says,  “earth  is  not  to  be  regarded  as  a vehicle 
for  the  inoffensive  removal  beyond  the  limits  of  the  toAvn  of  what 
has  hitherto  been  its  n)ost  troublesome  product,  but  as  a medium 
for  bringing  together  the  offensive  ingredients  of  this  product 
and  the  world’s  great  scavenger,  oxygen.  This  oxygen  does  its 
work  of  liberating  the  organic  elements  so  well  that,  according 
to  Professor  Voelcker,  “the  use  of  the  same  earth  four  or  five 
times  over,  although  perfectly  successful  in  accomplishing  the 
chief  purpose  of  deodorization,  fails  to  add  to  it  a sufficient 
amount  of  fertilizing  matter  to  make  it  an  available  commercial 


manure.' 


74 


SANITARY  ENGINEERING. 


This  agrees  with  the  analysis  previously  mentioned.  If  the 
earth  does  its  work  thoroughly,  the  manure  is  lost,  for,  in  truth, 
this  is  the  object  to  be  accomplished ; to  drive  the  organic  elements 
back  again,  uncombined,  or  at  least  in  harmless  combinations,  to 
the  air;  and  this  the  condensed  oxygen  accomplishes. 

One  advantage  of  the  system  is  that  the  privy  or  commode,’^ 
may  be  attached  to  the  house;  in  fact  the  best  earth-closets  may 
be  kept  in  the  chamber,  without  any  other  odor  being  perceived 
than  that  of  the  earth  used,  which  should  be  fine,  dry  and  sifted. 

This  dry-earth  system  is  familiar  to  soldiers  of  the  late  war, 
the  sinks  used  by  them  receiving  daily  a slight  covering  of  the 
very  earth  thrown  out  in  their  construction.  This  effectually 
prevented  deleterious  effects;  and  in  exact  accordance  with  the 
theory  and  facts  previously  adduced,  the  organic  matter  was  so 
soon  dissipated — when  the  system  was  carried  out  faithfully — 
that  the  earth  was  uot  worth  removal  as  manure.  This  fact  I 
know  from  experience;  and  it  agrees  with  all  other  experiments 
and  analyses  referring  to  this  point.  When  the  earth  covering 
is  too  slight,  or  it  is  neglected  at  times,  the  result  will  be  more 
manure  but  diminished  healthfulness.  There  can  be  no  hesita- 
tion in  the  choice.  • ' 

Where  the  dwelling  {)l;ice  contains  a garden,  the  used  earth 
may  be  put  on  it,  for  it  is  quite  probable  that  even  when  most, 
or  all  of  the  organic  matter,  has  been  driven  off,  that  the  chem- 
ical changes  effected  may  have  liberated  potash  or  soda,  etc.,  in 
the  original  soil,  thus  rendering  it  more  valuable  than  before  to 
plants. 

It  may  be  interesting  to  know  that  there  is  biblical  sanction 
for  this  method;  the  Israelites  being  required  to  carry  out  the 
system  whenever  they  went  outside  of  the  camp  to  ease  them- 
selves. (Deut.,  xxiii:  13). 

It  is  admitted  that  this  system  does  uot  admit  of  the  same 
public  control  as  the  preceding,  but  it  may  be  made  eminently 
serviceable  by  those  who  desire  it.  It  is  especially  applicable  to 
country  houses  and  the  smaller  villages. 


CONCLUSIONS. 


75 


I know  of  this  .system  being  carried  out  and  satisfying  tlie 
daily  wants  of  from  70  to  100  persons — the  room  being  almost 
entirely  free  from  odor  at  all  times.  If  sulphate  of  lime  is 
added,  it  fixes  the  ammonia  that  would  otherwise  be  driven  off, 
and  thus  renders  the  product  of  some  use  as  a fertilizer. 

When  epidemics  prevail,  then  in  addition  to  usual  methods  of 
sewage  disposal,  disinfectants  should  be  used,  as  to  which  see 
another  paper  issued  by  the  Board  of  Health  on  the  subject. 

CONCLUSIONS. 

In  taking  a retrospective  glance  at  what  has  preceded,  we  can- 
not but  be  impressed  with  the  beneficence  of  those  laws  that  tend, 
in  one  eternal  round,  to  the  purification  of  what  man  has  made 
unclean.  Foul  sewage  is  thrown  into  a crystal  stream,  whose 
hitherto  transparent  waters  now  blush  at  the  pollution.  She 
invokes  the  aid  of  the  ever-constant  winds  and  of  the  animal  and 
vegetable  life  she  bears  in  her  bosom.  They  respond,  and,  in 
time,  she  is  once  more  pure  and  undefiled.  The  pure  Avater  falls 
from  clouds,  cleanses  our  soil  and  passes  into  the  earth,  foul,  to 
again  issue  in  wells  or  springs,  generally  free  from  the  taint  of 
man^s  works. 

Mother  earth  condenses  gases  that  oxidize  and  liberate  noxious, 
waste  elements  in  harmless  combinations.  We  breathe  into  the 
air  a hurtful  gas;  but  the  winds  and  the  rains  bear  it  from  us, 
or  the  vegetation  reaches  out  its  leaves,  with  their  million  little 
mouths,  to  absorb  it  and  give  us  in  exchange  the  life-giving 
oxygen. 

Is  it  asking  too  much,  should  Nature  call  sometimes  for  man’s 
assistance  to  expedite  results,  in  order  that  he  may  add  to  his 
days  and  happiness?  If  not,  then  ponder  well  on  the  means 
that  have  been  proposed  to  assist  nature  in  her  work  of  purifica- 
tion and  act  on  them. 

It  is  not  intended  that  the  foregoing  brief  summary  of 
‘‘means”  is  complete.  It  was  not  intended  to  be,  though  funda- 
mental general  principles,  proper  to  be  known  at  present,  it  is 
hoped  have  been  stated  clearly  and  fairly. 


76 


SANITARY  ENGINEERING. 


The  object  of  such  papers  as  this  is  to  advise  the  public,  who 
cannot  be  thinking  all  the  time  about  sanitary  matters,  with 
regard  to  efficient  means  of  protection  against  sickness,  and  espe- 
cially against  epidemics.  The  county  boards  of  health  are 
looked  to  as  the  authorized  agents  in  introducing  more  effective 
sanitary  measures.  But  it  is  well  known  that  such  organizations 
cannot  go  far  ahead  of  public  opinion.  We  need  the  aid  of  the 
press,  the  great  educators  of  public  opinion,  to  assist  in  the  good 
fight  for  health. 

Let  some  of  the  systems  for  the  disposal  of  sewage  matters  be 
faithfully  carried  out  simultaneously  with  a proper  attention  to 
ventilation,  drainage,  water  supply,  and  the  general  cleanliness 
of  streets  and  yards,  and  it  is  believed  that  the  death-rate  will 
be  lowered  and  that  epidemics  will  be  almost  unknown. 

Let  every  open  privy  and  cess-pool  be  abolished  with  their 
pestilential  odors;  it  follows  that  the  source  of  contamination  of 
the  wells  will  be  gone,  and  that  zymotic  diseases  will  have  their 
usual  channels  of  attack  effectually  cut  off. 

Let  us,  then,  advance  towards  that  higher  civilization  which 
demands  pure  air  and  wholesome  water,  not  simply  as  a luxury 
to  be  enjoyed  only  on  the  cool  mountain’s  sides,  but  as  a neces- 
sity, to  be  enforced  in  city  and  village  by  stringent  laws  and 
requirements. 


APPENDIX  I. 


\ The  following  table  may  prove  a convenience  to  those  who  use 
cisterns.  It  gives  the  capacity  of  a cylindrical  cistern,  for  one 
foot  in  height,  and  the  diameters  given,  in  U.  S.  liquid  gallons 
(of  231  cubic  inches  each),  the  nearest  whole  number  being  taken : 


Diameter. 

Feet. 

Capacity. 

Gallons. 

Diameter. 

Feet. 

Capacity. 

Gallons. 

5 

147 

15 

1322 

6 

211 

16 

1504 

7 

288 

17 

1698 

8 

376 

18 

1903 

9 

476 

19. 

2121 

10 

587 

20 

2350 

11 

711 

21 

2591 

12 

846 

22 

2843 

13 

993 

23 

3108 

14 

1151 

24 

3384 

Multiply  these  tabular  numbers  by  the  height  of  the  cistern  in 
feet  to  get  the  capacity  of  a cistern  corresponding  to  that  height. 


APPENDIX  II. 


Through  the  courtesy  of  Dr.  Charles  F.  Folsom,  of  the  Mas- 
sachusetts Board  of  Health,  the  accompanying  wood-cuts  are  pre- 
sented— they  having  first  appeared  in  the  Massachusetts  Report 
of  the  Board  of  Health  for  1876. 

The  cuts  represent  in  order  the  natural  drainage  from  open 
privies  and  sinks,  into  wells  that  are  placed  too  near  them;  sec- 
tions of  common  privies  and  sink-hole,  both  polluting  the  soil 
around  them;  and  lastly,  three  plans  for  privies  based  upon  the 
dry-earth  system. 

It  is  to  be  observed  with  respect  to  the  latter,  that  the  con- 
ditions are  simply  that  the  pails  used  be  completely  under  cover 
and  placed  upon  a dry  foundation,  so  that  no  matter  from  the 
pails  shall  ever  reach  the  ground  below  them,  thereby  poisoning 
the  air  with  its  effluvia  and  the  wells  with  its  drainage. 

It  is  necessary  that  the  earth,  charcoal  or  ashes  be  kept  in  a 
dry  place  and  under  cover,  the  most  convenient  place  being  an 
apartment  just  to  the  rear  of  the  pails,  from  which  it  can  be 
readily  shovelled  into  the  pails  under  and  not  th7'ough  the  seats 
as  when  the  ashes,  etc.,  are  kept  in  the  privy-room  proper. 

An  ordinary  open  privy  can  generally  be  transformed  into  one 
closed  from  the  access  of  rain,  by  cutting  out  a space  in  the 
weather- boarding  of  the  back,  nearly  as  high  as  the  top  of  the 
seats,  and  replacing  this  boarding  by  a door  working  on  vertical 
or  horizontal  hinges,  as  shown  in  one  of  the  figures.  On  open- 
ing this  door,  the  half-barrels  or  pails  can  be  set  under  the  seats, 
and  every  morning  charcoal,  etc.,  can  be  thrown  over  the  con- 
tents so  as  to  keep  down  all  odor.  The  pails  should  be  set  upon 
a plank  or  stone  foundation — at  least  upon  a few  blocks  or  bricks 
— to  elevate  them  a few  inches' above  the  ground,  so  that  water 
may  not  reach  them.  As  the  pails  are  filled  they  should  be 


APPENDIX  II. 


79 


emptied  under  a shed  and  dry  earth,  etc.,  strewn  over  the  con- 
tents, the  action  of  which  in  destroying  the  organic  matter  has 
been  already  explained. 

Where  wells  are  at  a distance,  the  contents  of  the  pails  might 
be  emptied  on  cultivated  ground  for  their  manure,  a slight  cov- 
ering of  earth  being  again  used  to  keep  down  any  odor  that 
might  arise. 

It  must  be  borne  in  mind,  however,  that  although  soil  is  an 
excellent  filter  for  impure  or  infected  air,  that  may  pass  through 
it,  it  is  a very  poor  filter  for  infected  water  from  privies,  cess- 
pools and  sewers,  so  that  danger  of  contamination  of  wells  from 
these  sources,  particularly  when  deep  down  in  the  earth,  away 
from  its  oxidizing  tendencies,  needs  always  to  be  carefully 
guarded  against.  Such  filth-soaked  soils  may  take  ages  to 
purify  and  afford  good  drinking  water. 


80 


APPENDIX  II. 


• jio^  crpTL  ^njj.  J.0  Snpi. 


APPENDIX  II. 


81 


82, 


APPENDIX  II. 


Manchester  CorporcdiotL, 


APPENDIX  II. 


83 


84 


APPENDIX  II. 


Rochdale  Corporation 
Paitera  Fail  closet. 

td.  excremerLt  pail, 

Fash  iuJb. 

G.  scaicoym  {raised) 

D iron  collar  helorir  seat .reackinsr sh^ly into 
pail  rdie2i  corer  is  doryn. 

F,  hinyed  upright  of  seat 

CdDOvadmiiim^ftom-Ovisidc  toexcrcmcht pail 


APPENDIX  III. 


The  following  lucid  description  of  the  ventilation  of  the  State 
Lunatic  Asylum  of  New  York,  located  at  Utica,  New  York,  is 
taken,  by  permission  of  its  author.  Dr.  John  P.  Gray,  from  the 
‘^Thirty-sixth  Annual  Report  of  the  Managers  of  the  State 
Lunatic  Asylum.’’ 

It  is  prefaced  by  a short  extract  from  the  report : 

“ The  managers  consider  the  method  of  heating  and  ventila- 
tion of  the  institution  to  be  the  safest,  most  economical,  and  best. 
Information  is  frequently  sought  as  to  the  system  adopted.  Re- 
cently an  application  made  through  the  State  Department  by  the 
British  government  for  a detailed  statement  concerning  the  appli- 
ances and  method,  was  referred  to  Dr.  Gray,  the  superintendent 
of  this  institution,  who  made  a report  which  was  submitted  to 
this  board  before  transmission.  The  managers  deem  it  such  a 
clear  and  succinct  statement  of  the  method  adopted,  that  they 
embody  it  as  a document  worthy  of  permanent  record  for  use 
and  reference. 

MODE  OF  VENTILATING  AND  HEATING. 

1.  The  mode  of  ventilation  adopted  is  that  of  forcing  air  into 
the  building  by  the  use  of  two  centrifugal  fans,  a drawing  and 
description  of  which  accompany  this  communication. 

2.  The  air  is  delivered  from  the  fans  to  all  parts  of  the  build- 
ing. 

3.  First:  Into  the  large  channel  or  basement  air  duct,  or  air 
plenum,  which  is  continuous  under  the  whole  building. 

4.  Second : From  this  air  duct  or  air  plenum,  the  air  passes 
by  flues  into  the  various  wards  and  rooms  to  be  supplied.  Each 
flue  is  independent;  that  is,  it  has  an  exit  at  but  one  point. 


86 


APPENDIX  III. 


These  flues  open  into  the  wards  or  rooms  to  be  supplied  at  a 
point  above  the  level  of  the  top  of  the  windows  and  doors,  so 
that  no  air  movement  caused  by  opening  a windovs^  or  door  will 
disturb  the  current  of  the  incoming  air.  The  air  is  thus  dis- 
tributed uniformly  through  every  part  of  the  building. 

5.  From  the  corridors  and  rooms  flues  are  constructed,  start- 
ing just  above  the  base-board,  each  flue  passing  independently 
into  the  attic  air-chamber.  Over  part  of  the  building  there  is 
ridge  ventilation.  Over  other  parts  of  the  building  the  exit  is 
through  ventilators  fixed  at  regular  distances. 

6.  Each  fan  delivers  at  each  revolution  1,000  cubic  feet  of  air. 
They  can  be  driven  to  supply  almost  any  desired  quantity.  They 
are  here  driven  night  and  day,  and  supply  5,000,000  cubic  feet 
of  air  per  hour,  which  is  a little  over  100  cubic  feet  per  minute 
to  each  occupant  of  the  house  night  and  day. 

7.  The  main  air  duct  or  plenum  is  large  enough  to  contain 
any  quantity  of  air  desired,  without  the  need  of  a rapid  current. 
The  area  of  the  flues  leading  from  this  duct  to  the  wards  and 
rooms  is  equal  to  forty-two  inches  for  each  occupant.  The  exit 
flues  from  the  wards  and  rooms  to  the  attic  chamber  is  equal  to 
sixty-four  inches  for  each  occupant.  The  exit  area  through  the 
ridge  ventilation  and  ventilators  equals  seventy  inches  for  each 
occupant. 

8.  In  every  single  sleeping-room  there  is  a flue  for  the  exit  of' 
air  of  sixty-four  inches  area.  In  associate  sleeping-rooms  the 
area  of  the  several  flues  is  equal  to  sixty-four  inches  for  each 
occupant.  The  flues  for  the  supply  of  air  open  on  the  corridors 
at  the  height  already  stated.  The  sleeping-rooms  receive  the  air 
frotn  the  corridors  at  or  near  the  floor.  In  some  of  the  wards 
there  is  no  threshold  under  the  door,  and  the  doors  are  shortened 
at  the  bottom  to  allow  a space  between  them  and  the  floor  of 
sixty- HTur  inches  area.  In  some  the  air  enters  the  sleeping- rooms 
through  a register  in  the  bottom  rail  of  the  door.  In  the  asso- 
ciate sleeping-rooms,  where  sufficient  air  could  not  thus  be  ob- 
tained for  several  patients,  openings  are  made  through  the  walls 
at  points  near  the  floor.  In  a few  of  the  rooms  for  the  feeble 
the  flues  for  the  supply  of  air  open  into  the  rooms. 


APPENDIX  III. 


87 


9.  This  mode  secures  the  most  abundant  supply  of  fresh  air. 
It  secures  what  ventilation  means  practically:  that  is,  such  con- 
stant dilution  of  the  body  of  the  air  contained  in  the  building  by 
fresh  air  sent  in  as  to  make  it  for  all  practical  purposes  pure. 

10.  I do  not  use  the  words  ‘Afresh  and  foul  air  flues.^^  In 
reality,  this  method  secures  a constant  flow^  of  pure  air  through 
the  building  from  its  entrance  to  its  exit,  and  the  gradual  enlarge- 
ment of  the  areas  facilities  the  passage  and  exit  of  the  air,  and 
compensates  for  the  frictional  resistance  in  passing  through  the 
building. 

11.  It  is  stated  in  paragraph  four  that  the  air  is  introduced  at 
a height  above  the  doors  and  windows.  While  this  is  undoubt- 
edly best,  it  is  not  absolutely  necessary  to  success  in  ventilation. 
It  is  proper  to  say  that  in  a hospital  for  the  insane,  it  is  advisa- 
ble to  have  the  air  enter  above  a point  where  patients  would  be 
likely  to  throw  articles  into  the  flues,  and  also  to  avoid  the  evil 
of  patients  crowding  about  the  flues  and  impeding  the  thorough 
distributions  of  the  air.  In  the  offices  of  the  institution,  in  the 
residence  of  the  officers,  and  some  of  the  rooms  not  constantly 
used  in  the  hospital  proper,  the  air  is  introduced  just  above  the 
base-board,  and  in  some  instances  through  the  floor;  but  in  all 
cases,  no  matter  where  the  air  is  introduced,  the  exit  flues  should 
start  from  near  the  floor  as  already  described.  Where  the  air  is 
thus  introduced,  it  is  important  to  locate  the  flues  so  as  not  to 
have  them  opposite  windows. 

12.  Where  the  rooms  are  large,  as  in  case  of  parlors  and  sit- 
ting-rooms, and  require  two  or  more  flues  for  the  introduction 
and  exit  of  air,  it  is  important  to  distribute  them  so  that  all 
parts  of  the  rooms  shall  be  supplied  uniformly. 

13.  Heating  is  combined  with  ventilation.  The  air  is  warmed 
to  the  degree  required  by  being  compelled  to  pass  over  cast-iron 
raditors,  through  which  steam  is  circulated,  on  its  way  from  the 
fan  to  the  occupied  parts  of  the  building.  These  radiators  are 
placed  in  the  main  air  duct  or  plenum,  and  are  in  separate  blocks 
directly  underneath  the  flues  leading  from  this  duct  to  the  occu- 
pied parts  of  the  building.  There  is  a box  of  radiators  for  each 


88 


APPENDIX  III. 


set  of  three  flues,  one  flue  leading  to  each  story.  Each  block 
has  an  independent  connection  with  the  main  steam-pipe,  so  that 
each  block  can  be  used  separately.  Each  block  is  cased  in  on 
the  sides,  leaving  the  bottom  open  for  the  free  passage  of  air  over 
the  radiators.  By  this  arrangement  the  air  is  warmed  at  the 
nearest  point  of  its  delivery  for  use,  and  the  heat  is  not  wasted 
by  absorption  into  the  walls  of  a large  general  air-chamber,  and 
the  temperature  of  the  air  sent  into  any  special  part  of  the  build- 
ing can  be  regulated  as  may  be  desired,  simply  by  introducing 
more  or  less  steam  into  the  individual  blocks. 

14.  These  radiators  are  so  constructed  and  connected  as  to 
make  what  is  called  a steam  coil,^^  and  the  blocks  are  so 
arranged  and  connected  that  steam  can  be  turned  upon  one-third, 
two- thirds,  or  the  whole,  as  the  atmospheric  temperature  may 
require.  Of  course,  there  is  no  impediment  to  the  passage  of 
the  air  through  these  blocks  for  summer  ventilation  when  heat 
is  not  needed,  as  the  space  between  them  is  sufficient  for  the  pas- 
sage of  the  largest  volume  of  air  required. 

15.  This  large  body  of  air  entering  and  distributed  in  the 
manner  described  produces  no  appreciable  current.  It  is  not 
found  necessary  to  raise  the  temperature  of  the  air  introduced 
higher  than  100  degrees  at  the  point  of  entrance  to  the  wards 
and  rooms,  in  order  to  secure  a general  temperature  of  seventy 
degrees  throughout.  Thus  the  air  is  not  rarified,  expanded,  or 
dried,  to  a degree  that  interferes  with  healthfulness  and  comfort. 

16.  This  system  does  not  require  registers  to  control  the  tempe- 
rature of  the  room  by  closing  and  unclosing  them.  The  amount 
of  air  delivered  over  each  radiating  block  is  warmed  to  the  tem- 
perature there  required,  and  as  the  volume  of  the  air  delivered 
is  uniform  and  constant,  thorough  ventilation  is  obtained.  Reg- 
isters in  the  wards  of  a hospital  would  be  likely  to  be  used  to 
close  off  the  flow  of  air  if  it  was  too  warm,  that  being  easier 
done  than  to  give  information  to  the  engineer  having  control  of 
the  heating  blocks.  Registers  are  used  in  the  offices  and  resi- 
dences of  the  officers. 


APPENDIX  III. 


89 


17.  It  is  possible  to  determine  the  exact  amount  of  coal  neces- 
sary to  raise  a given  amount  of  atmosphere  one  degree,  and  this 
gives  the  key  to  the  necessary  amount  of  coal  to  be  burned  in  the 
steam-boilers  to  raise  the  whole  quantity  of  air  introduced  to  any 
desired  temperature.  The  engineer  by  observing  the  tempera- 
ture of  the  external  atmosphere,  and  knowing  the  volume  of  air 
delivered,  can,  with  sufficient  accuracy,  supply  the  necessary 
amount  of  heat. 

18.  To  illustrate:  The  cubic  capacity  of  the  wards  and  rooms 
of  this  asylum  is,  in  round  numbers,  about  5,000,000  feet.  Five 
million  cubic  feet  of  air  sent  in  by  the  fans  per  hour  night  and 
day.  Twelve  pounds  of  coal  will  raise  this  atmosphere  one 
degree  per  hour.  At  this  writing  the  average  outside  tempera- 
ture for  the  past  twenty-four  hours  has  been  ten  degrees  below 
zero.  The  temperature  of  the  wards  has  been  maintained  at 
from  seventy  to  seventy-two,  and  we  have  burned  8 tons  and 
1,280  pounds  of  coal,  an  average  of  720  pounds  per  hour;  the 
actual  number  of  occupants  722. 

DESCRIPTION  OF  FAN. 

The  fan  and  its  support  are  of  iron,  the  casing  of  wood ; the 
rotary  or  operating  part  of  the  fan  consists  of  a shaft  with  eight 
radial  arms  set  back  on  a curve  at  the  extremities  of  which  are 
fastened  iron  wind-boards,  three  feet  wide  and  five  feet  long,  in 
the  direction  of  the  axis;  the  extremities  of  the  wind-boards  are 
six  feet  from  the  center  and  consequently  describe  a circle  of 
twelve  feet  diameter.  The  shaft  extends  beyond  the  casing  and 
rests  on  pulley-blocks,  and  on  the  driving  side  it  is  lengthened 
six  feet  to  receive  the  driving-pulley  and  remove  all  obstruc- 
tion to  the  easy  entrance  of  air  to  the  fans;  the  motion  is 
imparted  by  a belt  passing  over  the  pulley,  four  feet  in  diameter, 
with  ten-inch  face,  on  the  end  of  the  shaft,  the  arms  and  boards 
revolve  within  the  wooden  casing,  the  circumference  of  which 
instead  of  being  concentric  with  the  shaft,  describes  a curve  of 
increasing  diameter  and  forms  outside  the  wind-boards  a chan- 
nel of  constantly  enlarging  capacity  towards  the  point  of  delivery. 


90 


APPENDIX  III. 


The  casing  is  therefore  scroll-shaped,  this  space  being  six  inches 
in  front  and  enlarging  to  three  feet  at  the  bottom.  The  height 
of  the  casing  from  the  floor  is  eighteen  feet.  The  cross-sectional 
area  is  equal  at  the  point  of  delivery  to  forty-two  square  feet. 
The  opening  in  each  side  of  the  fan-casing,  for  the  inlet  of  air, 
is  six  feet  in  area.  This  whole  machinery  is  placed  in  a room, 
the  floor  of  which  is  oh  a level  with  the  floor  of  the  main  air 
duct,  and  the  air  is  admitted  through  a large  open  space,  double 
the  area  of  both  inlets,  and  properly  guarded. 


THE  LIBRARY  OF  THE 

NOV  11 1938 

UNIVERSITY  OF  ILLINOIS- 


UNIVERSITY  OF  ILUNOI8-URBANA 


3 0112  049890053 


